Cochrane Database of Systematic Reviews

High-dose versus low-dose oxytocin infusion regimens for

induction of labour at term (Review)

Budden A, Chen LJY, Henry A

Budden A, Chen LJY, Henry A.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term.
Cochrane Database of Systematic Reviews 2014, Issue 10. Art. No.: CD009701.
DOI: 10.1002/14651858.CD009701.pub2.

www.cochranelibrary.com

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review)
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 TABLE OF CONTENTS
HEADER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
PLAIN LANGUAGE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
AUTHORS’ CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
CHARACTERISTICS OF STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
DATA AND ANALYSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Analysis 1.1. Comparison 1 High- versus low-dose oxytocin, Outcome 1 Vaginal delivery not achieved within 24 hours. 39
Analysis 1.2. Comparison 1 High- versus low-dose oxytocin, Outcome 2 Caesarean section. . . . . . . . . . 40
Analysis 1.3. Comparison 1 High- versus low-dose oxytocin, Outcome 3 Serious neonatal morbidity or perinatal death. 41
Analysis 1.4. Comparison 1 High- versus low-dose oxytocin, Outcome 4 Serious maternal morbidity or death. . . 41
Analysis 1.5. Comparison 1 High- versus low-dose oxytocin, Outcome 5 Time from induction to delivery. . . . . 42
Analysis 1.6. Comparison 1 High- versus low-dose oxytocin, Outcome 6 Uterine hyperstimulation, fetal heart rate changes
not specified. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Analysis 1.7. Comparison 1 High- versus low-dose oxytocin, Outcome 7 Uterine rupture. . . . . . . . . . . 44
Analysis 1.8. Comparison 1 High- versus low-dose oxytocin, Outcome 8 Epidural analgesia. . . . . . . . . . 44
Analysis 1.9. Comparison 1 High- versus low-dose oxytocin, Outcome 9 Instrumental birth. . . . . . . . . . 45
Analysis 1.10. Comparison 1 High- versus low-dose oxytocin, Outcome 10 Apgar score less than seven at five minutes. 46
Analysis 1.11. Comparison 1 High- versus low-dose oxytocin, Outcome 11 Perinatal death. . . . . . . . . . 47
Analysis 1.12. Comparison 1 High- versus low-dose oxytocin, Outcome 12 Postpartum haemorrhage. . . . . . 47
Analysis 1.13. Comparison 1 High- versus low-dose oxytocin, Outcome 13 Endometritis. . . . . . . . . . . 48
Analysis 2.1. Comparison 2 High- versus low-dose oxytocin: previous caesarean section or not, Outcome 1 Caesarean
section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Analysis 3.1. Comparison 3 High- versus low-dose oxytocin: nulliparity or parity, Outcome 1 Uterine hyperstimulation,
fetal heart rate changes not specified. . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Analysis 3.2. Comparison 3 High- versus low-dose oxytocin: nulliparity or parity, Outcome 2 Caesarean section. . . 51
Analysis 4.1. Comparison 4 High- versus low-dose oxytocin: cervix unfavourable, favourable, or undefined, Outcome 1
Caesarean section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Analysis 5.1. Comparison 5 High- versus low-dose oxytocin: excluding studies at high risk of bias, Outcome 1 Caesarean
section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Analysis 5.2. Comparison 5 High- versus low-dose oxytocin: excluding studies at high risk of bias, Outcome 2 Induction to
delivery interval. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Analysis 5.3. Comparison 5 High- versus low-dose oxytocin: excluding studies at high risk of bias, Outcome 3 Uterine
hyperstimulation, fetal heart rate changes not specified. . . . . . . . . . . . . . . . . . . . 54
WHAT’S NEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
CONTRIBUTIONS OF AUTHORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
DECLARATIONS OF INTEREST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
SOURCES OF SUPPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
DIFFERENCES BETWEEN PROTOCOL AND REVIEW . . . . . . . . . . . . . . . . . . . . . 55
INDEX TERMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) i
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
[Intervention Review]

High-dose versus low-dose oxytocin infusion regimens for

induction of labour at term

Aaron Budden1 , Lily JY Chen2 , Amanda Henry3

1 Obstetrics and Gynaecology, Royal Hospital for Women, Randwick, Australia; The University of New South Wales, Sydney, Australia.
2 Bankstown-Lidcombe Hospital, Sydney, Australia. 3 School of Women’s and Children’s Health, University of New South Wales,
Randwick, Australia

Contact address: Aaron Budden, Obstetrics and Gynaecology, Royal Hospital for Women, Barker Street, Randwick, NSW, 2034,
Australia. aaron.budden@sesiahs.health.nsw.gov.au, a.budden@unsw.edu.au.

Editorial group: Cochrane Pregnancy and Childbirth Group.

Publication status and date: Edited (no change to conclusions), published in Issue 3, 2016.

Citation: Budden A, Chen LJY, Henry A. High-dose versus low-dose oxytocin infusion regimens for induction of labour at term.
Cochrane Database of Systematic Reviews 2014, Issue 10. Art. No.: CD009701. DOI: 10.1002/14651858.CD009701.pub2.

Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

ABSTRACT

Background

When women require induction of labour, oxytocin is the most common agent used, delivered by an intravenous infusion titrated to
uterine contraction strength and frequency. There is debate over the optimum dose regimen and how it impacts on maternal and fetal
outcomes, particularly induction to birth interval, mode of birth, and rates of hyperstimulation. Current induction of labour regimens
include both high- and low-dose regimens and are delivered by either continuous or pulsed infusions, with both linear and non-linear
incremental increases in oxytocin dose. Whilst low-dose protocols bring on contractions safely, their potentially slow induction to birth
interval may increase the chance of fetal infection and chorioamnionitis. Conversely, high-dose protocols may cause undue uterine
hyperstimulation and fetal distress.

Objectives

To determine the effectiveness and safety of high- versus low-dose oxytocin for induction of labour at term

Search methods

We searched the Cochrane Pregnancy and Childbirth Group’s Trials Register (31 August 2014) and the reference lists of relevant papers.

Selection criteria

Randomised controlled trials and quasi-randomised controlled trials that compared oxytocin protocol for induction of labour for
women at term, where high-dose oxytocin is at least 100 mU oxytocin in the first 40 minutes, with increments delivering at least
600 mU in the first two hours, compared with low-dose oxytocin, defined as less than 100 mU oxytocin in the first 40 minutes, and
increments delivering less than 600 mU total in the first two hours.

Data collection and analysis

Two review authors independently assessed study eligibility, extracted data and assessed the risk of bias of included studies. Data were
checked for accuracy.
High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 1
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Main results

We have included nine trials, involving 2391 women and their babies in this review. Trials were at a moderate to high risk of bias overall.

Results of primary outcomes revealed no significant differences in rates of vaginal delivery not achieved within 24 hours (risk ratio (RR)
0.94, 95% confidence interval (CI) 0.78 to 1.14, two trials, 1339 women) or caesarean section (RR 0.96, 95% CI 0.81 to 1.14, eight
trials, 2023 women). There was no difference in serious maternal morbidity or death (RR 1.24, 95% CI 0.55 to 2.82, one trial, 523
women), and no difference in serious neonatal morbidity or perinatal death (RR 0.84, 95% CI 0.23 to 3.12, one trial, 781 infants).
Finally, no trials reported on the number of women who had uterine hyperstimulation with fetal heart rate changes.

Results of secondary outcomes revealed no difference between time from induction to delivery (mean difference (MD) -0.90 hours,
95% CI -2.28 to +0.49 hours; five studies), uterine rupture (RR 3.10, 95% CI 0.50 to 19.33; three trials), epidural analgesia (RR 1.03,
95% CI 0.89 to 1.18; two trials), instrumental birth (RR 1.22, 95% CI 0.88 to 1.66; three trials), Apgar less than seven at five minutes
(RR 1.25, 95% CI 0.77 to 2.01, five trials), perinatal death (RR 0.84, 95% CI 0.23 to 3.12; two trials), postpartum haemorrhage (RR
1.08, 95% CI 0.87 to 1.34; five trials), or endometritis (RR 1.35, 95% CI 0.53 to 3.43; three trials). Removal of high bias studies reveals
a significant reduction of induction to delivery interval (MD -1.94 hours, 95% CI -0.99 to -2.89 hours, 489 women). A significant
increase in hyperstimulation without specifying fetal heart rate changes was found in the high-dose group (RR 1.86, 95% CI 1.55 to
2.25).

No other secondary outcomes were reported: unchanged/unfavourable cervix after 12 to 24 hours, meconium-stained liquor, neonatal
intensive care unit admission, neonatal encephalopathy, disability in childhood, other maternal side-effects (nausea, vomiting, diarrhoea),
maternal antibiotic use, maternal satisfaction, neonatal infection and neonatal antibiotic use.

Authors’ conclusions

The findings of our review do not provide evidence that high-dose oxytocin increases either vaginal delivery within 24 hours or the
caesarean section rate. There is no significant decrease in induction to delivery time at meta-analysis but these results may be confounded
by poor quality trials. High-dose oxytocin was shown to increase the rate of uterine hyperstimulation but the effects of this are not
clear. The conclusions here are specific to the definitions used in this review. Further trials evaluating the effects of high-dose regimens
of oxytocin for induction of labour should consider all important maternal and infant outcomes.

PLAIN LANGUAGE SUMMARY

High-dose versus low-dose oxytocin infusion regimens for induction of labour

Some women do not begin labour spontaneously and may need assistance. This assistance, known as induction of labour, involves
the use of an intervention to artificially commence uterine contractions for the mother. Oxytocin is a drug that is commonly given to
women for induction of labour; however the most suitable dose to enable birth to occur safely for the mother and her baby, within a
reasonable timeframe, is not known.

We included nine randomised controlled trials involving 2391 women and their babies in this review. The trials were of moderate
quality overall. All trials compared giving women a high dose versus a low dose of oxytocin for induction of labour. We found that
women who had a high dose of oxytocin were not more likely to have a shorter induction to delivery interval or have a vaginal birth
within 24 hours of receiving the treatment than women receiving a low dose of oxytocin. When poor-quality trials are removed from
analysis however, the induction to delivery interval was significantly shorter with high-dose oxytocin compared to low-dose oxytocin.
The likelihood of having a caesarean was similar with the different doses of oxytocin for induction of labour. No differences were
shown between the two groups of women in terms of serious complications, including death of the mother or her baby but women
receiving the high-dose oxytocin did have an increased risk of excessive uterine contractions (known as uterine hyperstimulation). No
trials provided any information about the number of women with uterine hyperstimulation with changes in the babies’ heart rate.
Similarly, no trials assessed satisfaction of the mother or her caregivers.

The trials were at moderate to high risk of bias overall. The definition of high- and low-dose protocols and the outcomes measured
varied considerably across the trials. The current evidence is not strong enough to recommend high-dose over low-dose regimens for
routine induction of labour. We recommend that further research is carried out.
High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 2
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
BACKGROUND cations, and mild placental abruption through to less immediately
threatening conditions, such as post date gestations and prolonged
Sometimes it is necessary to artificially induce labour when ma-
rupture of membranes.
ternal or fetal risks of continuing the pregnancy outweigh risks
of induction (Pakta 2005; WHO 2011). Oxytocin is the most
common induction agent used worldwide (Alfirevic 2009). It is a
neurohypophyseal hormone that belongs to the class of oxytocics, Description of the intervention
and is used to cause regular co-ordinated contractions from the The aim of induction of labour is to achieve an uncomplicated
fundus to cervix. During induction of labour it is given as an in- vaginal delivery within a reasonable time frame while avoiding
creasing infusion, titrated to the strength and frequency of uterine adverse events, such as hyperstimulation, chorioamnionitis, fetal
contractions (Rang 2007). distress, instrumental birth, postpartum haemorrhage, and cae-
sarean section. Oxytocin is used to stimulate contractions in order
Many pre-induction factors can influence the outcome of labour
to induce labour and achieve birth more quickly than would occur
induction; maternal factors include weight, parity, prior mode of
without its use. Current oxytocin regimens consist of either linear
delivery, and cervical favourability as classified by Bishop’s score,
or non-linear incremental increases. Low-dose regimens consist
whilst fetal factors include weight and gestational age (Crane
of oxytocin 0.5 to 2.0 mU/min starting dose with incremental
2006; Pakta 2005). Uncertainty exists regarding how the oxytocin
increase by 1.0 to 2.0 mU/min every 15 to 60 minutes (Pakta
dose regimen for induction of labour leads to the likelihood of a
2005). High-dose regimens have starting doses of oxytocin 2.0
successful vaginal delivery and adverse outcomes.
to 6.0 mU/min and incremental increases of 2.0 to 6.0 mU/min
In 2011, Kenyon et al published a Cochrane review on the effects every 15 to 40 minutes (Pakta 2005).
of high- versus low-dose oxytocin for augmentation of labour (
Kenyon 2011). The authors concluded that high-dose oxytocin
regimens were associated with a reduction in the length of labour How the intervention might work
and in caesarean section, and an increase in spontaneous vaginal
Research examining the difference between ’physiological’ (mim-
delivery, but these were not significant after adjusting for high-
icking endogenous level) and ’pharmacological’ (interventional
risk studies. These results should be considered in the context of
level) oxytocin doses demonstrated that ’pharmacological’ doses
achieving birth after a spontaneous labour has occurred, but it
lead to shorter induction to delivery time, with significantly fewer
can not be assumed that these findings also apply to induction of
labours lasting greater than 12 hours (Toaff 1978). The extremely
labour.
low ’physiological’ dose was ceased in common use in favour of 1.0
This review is one of a series of reviews of the methods of labour in- to 2.0 mU/min doubled every 15 to 20 minutes until Seitchik et al
duction using a standardised protocol. For more detailed informa- (Seitchik 1982) demonstrated women augmented with computer-
tion on the rationale for this methodological approach, please re- controlled ’low-dose’ regimens had a shorter time from augmen-
fer to the currently published ’generic’ protocol (Hofmeyr 2009). tation to full dilatation, and the infusion was decreased or ceased
The generic protocol describes how a number of standardised re- less often. This stimulated controversy regarding high- versus low-
views will be combined to compare various methods of preparing dose regimens, as some clinicians extrapolated these findings for
the cervix and inducing labour. induction of labour as well as augmentation. There is still ongoing
debate about risks versus benefits of using high- or low-dose reg-
imens. Previous studies suggest that high-dose regimens can lead
Description of the condition to shorter induction to delivery time and fewer failed inductions,
but at the expense of increased rates of hyperstimulation and fe-
Induction of labour is a commonly used term to group the pro-
tal distress requiring cessation of oxytocin, caesarean section, in-
cesses of cervical ripening, artificial rupture of membranes, and the
strumental birth, and postpartum haemorrhage (Hourvitz 1996;
initiation and augmentation of contractions. Induction of labour,
Pakta 2005; Satin 1992; Xenakis 1995).
however, is more accurately described as the artificial initiation of
uterine contractions before the spontaneous onset of labour (Pakta
2005), whilst augmentation refers to the stimulation of sponta-
neous but inadequate contractions (Wei 2010). In high-income
Why it is important to do this review
countries, up to 25% of all deliveries at term involve induction Low doses of oxytocin bring on contractions slowly though safely.
of labour; in developing countries, rates are generally lower but Whilst high doses cause contractions to occur sooner they can
variable, and in some settings are as high as those of high-income cause hyperstimulation or sustained contractions that can impair
countries (WHO 2011). There are many indications for induction blood flow to the placenta and hence cause fetal distress. Further
of labour. These encompass immediate problems, such as preg- adverse effects of high total doses of oxytocin include hypoten-
nancy-associated hypertensive diseases, maternal medical compli- sion with reflex tachycardia, water retention, and hyponatraemia

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 3
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
(Rang 2007). Conversely, the increased induction to delivery in- over of groups, for example, low-dose regimens starting at 0.5 to
terval that may occur with low-dose regimens increases the chance 2.0 mU/min with an incremental increase by 1.0 to 2.0 mU/min
for fetal infection and chorioamnionitis. It is important to deter- every 15 to 60 minutes, and high-dose regimens starting at 2.0
mine whether high-dose regimens can lead to shorter induction to to 6.0 mU/min and incremental increases of 2.0 to 6.0 mU/min
delivery times without an excess rate of adverse events compared every 15 to 40 minutes). Therefore, we chose to include two time
to low-dose regimens. references to allow differentiation of the groups. The first time
point is based on oxytocin reaching a steady state at approximately
40 minutes (Rang 2007). The choice of two hours as a second
time point is based on an arbitrary decision.
OBJECTIVES Other induction agents could be used in conjunction with the
oxytocin as long as both groups received the other induction agent
To determine, from the best available evidence, the effectiveness in a pre-specified manner.
and safety of high- versus low-dose oxytocin for induction of
labour at term (37 completed weeks’ gestation and beyond).
Types of outcome measures
Clinically relevant outcomes for trials of methods of cervical ripen-
METHODS ing/labour induction have been pre-specified by two authors of
Cochrane labour induction reviews (Justus Hofmeyr and Zarko
Alfirevic). As per the induction of labour protocol (Hofmeyr
2009), we examined five primary outcomes most representative of
Criteria for considering studies for this review
clinical effectiveness, complications, and satisfaction.

Types of studies Primary outcomes

All randomised and quasi-randomised controlled trials. We Five primary outcomes were chosen as being most representative
planned to include published and unpublished trials, as well as of the clinically important measures of effectiveness and compli-
studies presented only as abstracts. We planned to exclude cross- cations.
over trials. 1. Vaginal delivery not achieved within 24 hours (or period
specified by trial authors).
Types of participants 2. Uterine hyperstimulation with fetal heart rate (FHR)
changes.
Pregnant women for induction of labour carrying a viable fetus
3. Caesarean section.
from 37 weeks of completed gestation. Induction of labour refers
4. Serious neonatal morbidity or perinatal death (e.g. seizures,
to the artificial initiation of uterine contractions before the spon-
birth asphyxia defined by trialists, neonatal encephalopathy,
taneous onset of labour (as distinct from augmentation of labour
disability in childhood).
for delay or slow progress in labour as studied by Kenyon et al in
5. Serious maternal morbidity or death (e.g. uterine rupture,
Kenyon 2011).
admission to intensive care unit, septicaemia).
Perinatal and maternal morbidity and mortality are composite
Types of interventions outcomes. This is not an ideal solution because some components
High starting and continuing dose of oxytocin for the induction are clearly less severe than others. It is possible for one intervention
of labour compared with low dose. We have defined the dose to cause more deaths but less severe morbidity. However, in the
regimens as follows. context of labour induction at term, this is unlikely. All of these
• High-dose regimen: infusion to deliver more than 100 mU events are rare, and a modest change in their incidence is easier
oxytocin in the first 40 minutes and more than 600 mU in two to detect if composite outcomes are presented. The incidence of
hours individual components was explored as secondary outcomes.
• Low-dose regimen: infusion to deliver less than 100 mU
oxytocin in the first 40 minutes and less than 600 mU in two Secondary outcomes
hours
The choice of high and low dose was based on the starting and in-
cremental infusions previously used (Hourvitz 1996; Pakta 2005; Measures of effectiveness
Satin 1991; Xenakis 1995). As seen in these studies the variation 1) Time from induction of labour to delivery.
in starting dose and incremental increase can lead to some cross- 2) Cervix unfavourable/unchanged after 12 to 24 hours.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 4
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Complications 4. handsearches of 30 journals and the proceedings of major
3) Uterine hyperstimulation without FHR changes. conferences;
4) *Uterine rupture. 5. weekly current awareness alerts for a further 44 journals
5) Epidural analgesia. plus monthly BioMed Central email alerts.
6) Instrumental vaginal delivery. Details of the search strategies for CENTRAL, MEDLINE and
7) Meconium-stained liquor. Embase, the list of handsearched journals and conference pro-
8) Apgar score less than seven at five minutes. ceedings, and the list of journals reviewed via the current aware-
9) Neonatal intensive care unit admission. ness service can be found in the ‘Specialized Register’ section
10) Neonatal encephalopathy. within the editorial information about the Cochrane Pregnancy
11) Perinatal death. and Childbirth Group.
12) Disability in childhood. Trials identified through the searching activities described above
13) Maternal side-effects (all). are each assigned to a review topic (or topics). The Trials Search
14) Maternal nausea. Co-ordinator searches the register for each review using the topic
15) Maternal vomiting. list rather than keywords.
16) Maternal diarrhoea.
17) Other maternal side-effects: Searching other resources
- postpartum haemorrhage (as defined by the trial authors); We searched the bibliographies of relevant papers.
- serious maternal complications (e.g., intensive care unit admis- We did not apply any language restrictions.
sion, septicaemia but excluding uterine rupture);
- maternal death.
18) Neonatal infection.
Data collection and analysis
19) Neonatal antibiotics.
20) Chorioamnionitis.
21) Endometritis. Selection of studies
22) Maternal antibiotics.
Two review authors independently assessed for inclusion all the
potential studies we identified as a result of the search strategy. We
Measure of satisfaction resolved any disagreement through discussion, or if required, by
consultation with the third review author.
23) Woman not satisfied.
24) Caregiver not satisfied.
*’Uterine rupture’ included all clinically significant ruptures of un- Data extraction and management
scarred or scarred uteri. Trivial scar dehiscence noted incidentally We designed a form to extract data. For eligible studies, two review
at the time of surgery was excluded. authors extracted the data independently using the agreed form.
While all the above outcomes were sought, only those with data We resolved discrepancies through discussion or, if required, by
appear in the analysis tables. consultation with the third author. Data were entered into Re-
view Manager software (RevMan 2014) and checked for accuracy.
When information regarding any of the above was unclear, we
attempted to contact authors of the original reports to provide
Search methods for identification of studies further details.

Assessment of risk of bias in included studies

Electronic searches
Two review authors independently assessed risk of bias for each
We searched the Cochrane Pregnancy and Childbirth Group’s Tri-
study using the criteria outlined in the Cochrane Handbook for Sys-
als Register by contacting the Trials Search Co-ordinator (31 Au- tematic Reviews of Interventions (Higgins 2011). Any disagreement
gust 2014).
was resolved by discussion or by involving a third assessor.
The Cochrane Pregnancy and Childbirth Group’s Trials Register
is maintained by the Trials Search Co-ordinator and contains trials
identified from: (1) Sequence generation (checking for possible selection
1. quarterly searches of the Cochrane Central Register of bias)
Controlled Trials (CENTRAL); We described for each included study the method used to generate
2. weekly searches of MEDLINE; the allocation sequence in sufficient detail to allow an assessment
3. weekly searches of Embase; of whether it should produce comparable groups.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 5
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
We assessed the method as: Where sufficient information was reported, or could be supplied
• low risk of bias (any truly random process, e.g. random by the trial authors, we re-included missing data in the analyses
number table; computer random number generator); which we undertook. We assessed the methods as:
• high risk of bias (any non-random process, e.g. odd or even • low risk of bias (e.g. no missing outcome data; missing
date of birth; hospital or clinic record number); outcome data balanced across groups);
• unclear risk of bias. • high risk of bias (e.g. numbers or reasons for missing data
imbalanced across groups; ‘as treated’ analysis done with
substantial departure of intervention received from that assigned
(2) Allocation concealment (checking for possible selection
at randomisation);
bias)
• unclear risk of bias.
We described for each included study the method used to con-
ceal allocation to interventions prior to assignment and assessed
whether intervention allocation could have been foreseen in ad- (5) Selective reporting bias
vance of, or during recruitment, or changed after assignment. We described for each included study how we investigated the
We assessed the methods as: possibility of selective outcome reporting bias and what we found.
• low risk of bias (e.g. telephone or central randomisation; We assessed the methods as:
consecutively numbered sealed opaque envelopes); • low risk of bias (where it is clear that all of the study’s pre-
• high risk of bias (open random allocation; unsealed or non- specified outcomes and all expected outcomes of interest to the
opaque envelopes, alternation; date of birth); review were reported);
• unclear risk of bias. • high risk of bias (where not all the study’s pre-specified
outcomes were reported; one or more reported primary
(3.1) Blinding of participants and personnel (checking for outcomes were not pre-specified; outcomes of interest were
possible performance bias) reported incompletely and so could not be used; study failed to
include results of a key outcome that would have been expected
We described for each included study the methods used, if any, to
to have been reported);
blind study participants and personnel from knowledge of which
• unclear risk of bias.
intervention a participant received. Studies were judged to be at
low risk of bias if they were blinded, or if we judged that the lack of
blinding could not have affected the results. Blinding was assessed (6) Other sources of bias
separately for different outcomes or classes of outcomes. We described for each included study any important concerns we
We assessed the methods as: had about other possible sources of bias.
• low, high or unclear risk of bias for participants; We assessed whether each study was free of other problems that
• low, high or unclear risk of bias for personnel. could put it at risk of bias:
• low risk of other bias;
(3.2) Blinding of outcome assessment (checking for possible • high risk of other bias;
detection bias) • unclear whether there is risk of other bias.
We described for each included study the methods used, if any, to
blind outcome assessors from knowledge of which intervention a (7) Overall risk of bias
participant received. We assessed blinding separately for different We made explicit judgements about whether studies were at high
outcomes or classes of outcomes. risk of bias, according to the criteria given in the Cochrane Hand-
We assessed methods used to blind outcome assessment as: book for Systematic Reviews of Interventions (Higgins 2011). With
• low, high or unclear risk of bias. reference to (1) to (6) above, we assessed the likely magnitude and
direction of the bias and whether we considered it is likely to im-
(4) Incomplete outcome data (checking for possible attrition pact on the findings. We explored the impact of the level of bias
bias through withdrawals, dropouts, protocol deviations) through undertaking sensitivity analyses - see Sensitivity analysis.
We described for each included study, and for each outcome or
class of outcomes, the completeness of data including attrition Measures of treatment effect
and exclusions from the analysis. We stated whether attrition and
exclusions were reported, the numbers included in the analysis at
each stage (compared with the total randomised participants), rea- Dichotomous data
sons for attrition or exclusion where reported, and whether miss- For dichotomous data, we have presented results as summary risk
ing data were balanced across groups or were related to outcomes. ratio with 95% confidence intervals.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 6
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Continuous data Data synthesis
For continuous data, we have used the mean difference where out- We carried out statistical analysis using the Review Manager soft-
comes were measured in the same way between trials. We planned ware (RevMan 2014). We used fixed-effect meta-analysis for com-
to use the standardised mean difference to combine trials that mea- bining data where it was reasonable to assume that studies were
sured the same outcome, but used different methods. estimating the same underlying treatment effect: i.e. where tri-
als were examining the same intervention, and the trials’ popula-
tions and methods were judged sufficiently similar. Where there
Unit of analysis issues
was clinical heterogeneity sufficient to expect that the underlying
treatment effects differed between trials, or where substantial sta-
tistical heterogeneity was detected, we used random-effects meta-
Cross-over trials
analysis to produce an overall summary, if an average treatment
Cross-over trials were not included as it was believed that design effect across trials was considered clinically meaningful. The ran-
would compromise accurate assessment of the effect of interven- dom-effects summary was treated as the average range of possible
tions on the outcome measures. treatment effects and we have discussed the clinical implications
of treatment effects differing between trials. If the average treat-
Cluster-randomised trials
ment effect had not been clinically meaningful, we would not have
combined trials. Where we have used random-effects analyses, the
We did not include cluster-randomised trials. results have been presented as the average treatment effect with
95% confidence intervals, and the estimates of T² and I².
More than two treatment groups
For multi-armed trials, where two or more arms fit either our Subgroup analysis and investigation of heterogeneity
definition of “high dose” or “low dose”, we planned to pool the
results for analysis from the arms that fit our high-dose or low- If we had identified substantial heterogeneity, we planned to in-
dose definitions. vestigate it using subgroup analyses and sensitivity analyses. We
planned to consider whether an overall summary was meaningful,
and if it was, used random-effects analysis to produce it. Forest
Dealing with missing data plots showing results of the included studies with suppression of
For included studies, we noted levels of attrition. We planned to the pooled estimate were used for displaying outcomes where the
explore the impact of including studies with high levels of missing included studies reporting on those outcomes were felt to be too
data in the overall assessment of treatment effect using sensitiv- heterogeneous for a pooled estimate to be meaningful.
ity analysis. For all outcomes analyses were carried out, as far as Pre-dened subgroup analyses were:
possible, on an intention-to-treat basis, i.e. we attempted to in- • previous caesarean section or not;
clude all participants randomised to each group in the analyses. • nulliparity or parity;
The denominator for each outcome in each trial was the number • membranes intact or ruptured; and
randomised minus any participants whose outcomes were known • cervix unfavourable, favourable, or undefined.
to be missing.
We assessed subgroup differences by interaction tests available in
within RevMan (RevMan 2014). We included only primary out-
Assessment of heterogeneity comes in subgroup analyses. We have reported the results of the
We assessed statistical heterogeneity in each meta-analysis using subgroup analysis quoting the Chi² statistic and P value, and the
the T², I² and Chi² statistics. We regarded heterogeneity as sub- interaction test I² value.
stantial if an I² was greater than 30% and either a T² was greater
than zero, or there was a low P value (less than 0.10) in the Chi²
Sensitivity analysis
test for heterogeneity.
We carried out sensitivity analysis to explore the effect of trial
quality using the primary outcomes stated above. This involved
Assessment of reporting biases analysis of selection bias, performance bias and attrition bias. In
In future updates of this review, if there are 10 or more studies the analysis, we excluded studies rated as ’high risk of bias’ in
in the meta-analysis, we will investigate reporting biases (such as order to assess for any substantive difference to the overall result.
publication bias) using funnel plots. We will assess funnel plot Initially, we conducted the meta-analysis using all studies and then
asymmetry visually. If asymmetry is suggested by a visual assess- compared this to a meta-analysis where poorer quality studies were
ment, we will perform exploratory analyses to investigate it. excluded.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 7
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
RESULTS 2012; Durodola 2005; Fitzpatrick 2012; Gibb 1985; Girard 2009;
Goni 1995; Gungorduk 2011; Lazor 1993; Li 1996; Manjula
2014; Muller 1992; Odem 1988; Oral 2003; Parashi 2005; Parpas
Description of studies 1995; Pavlou 1978; Reid 1995; Ross 1998; Satin 1994; Ustunyurt
2007), and five are awaiting further classification (awaiting contact
from trialists to allow further assessment for inclusion) (Ashworth
Results of the search 1988; Raymond 1989; Salamalekis 2000; Singh 1993; Sotunsa
The search of the Cochrane Pregnancy and Childbirth Group’s 2013).
Trials Register retrieved 44 reports, relating to 38 studies. Of these Through searching the bibliographies of studies identified in the
studies, eight were included (Crane 1993; Dunn 1998; Hourvitz trial search, we identified a further six studies. We included one of
1996; Lowensohn 1990; Merrill 1999; Satin 1991; Tribe 2012; the trials (Orhue 1993), and excluded the other five studies (Chua
Willcourt 1994), 25 were excluded (Auner 1993; Blakemore 1990; 1991; Mercer 1991; Orhue 1993b; Orhue 1994; Steer 1985). See
Compitak 2002; Cummiskey 1990; Daniel-Spiegel 2004; Diven Figure 1.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 8
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Figure 1. Study flow diagram.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 9
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 were minimal women under 37 weeks. The categorisation of in-
Included studies
duction or augmentation was strictly based on cervical dilatation
Nine trials (Crane 1993; Dunn 1998; Hourvitz 1996; Lowensohn (less or more than 3 cm) and the frequency of contractions (more
1990; Merrill 1999; Orhue 1993; Satin 1991; Tribe 2012; or less than 10 contractions per hour), regardless of any cervical
Willcourt 1994) involving 2391 women and their babies have been ripening used. Tribe 2012 enrolled women over 18 years old re-
included in this review (see Characteristics of included studies for quiring oxytocin for stimulation after receiving prostaglandin E2
further details). and those with prolonged rupture of membranes without contrac-
tions. Women were excluded if induction was for fetal death in
utero, fetal abnormality, breech, multiple pregnancy, or previous
Infusion protocols caesarean section. In the Orhue 1993 trial, women with parity
There was considerable variation in how authors defined high- of five or more requiring induction were included. They were ex-
and low-dose protocols, as well as the outcome measures, through- cluded if there was intrauterine death, multiple pregnancy, previ-
out the included trials. In the trials by Crane 1993, Dunn 1998, ous caesarean section, previous uterine surgery, breech presenta-
Lowensohn 1990, Satin 1991 and Willcourt 1994 the difference tion, or borderline contracted pelvis on pelvimetry.
between their defined high- and low-dose protocol used a combi-
nation of higher oxytocin dose increases as well as shorter time in-
tervals between dose increases. The trial by Willcourt 1994 com- Outcomes
pared three groups, a high-dose continuous, a low-dose continu- Data were available for the following primary outcomes: vaginal
ous, and a low-dose pulsed group, with a large difference in doses delivery rates (two studies); caesarean section (eight studies); se-
between the low-dose and the pulse groups (36.8 mU versus 5.36 rious neonatal morbidity or perinatal death (one study); serious
mU at 40 minutes, 277.1 mU versus 56.08 mU at two hours), maternal morbidity or death (one study). No studies reported on
however they reported comparisons between the pulsed group and the primary outcome of uterine hyperstimulation with fetal heart
each of the continuous groups. In the Hourvitz 1996 and Merrill rate changes.
1999 trials, initial and subsequent oxytocin doses varied between The secondary outcome measures varied greatly between studies
groups, whilst the time between incremental increases was kept the as well as author definitions of outcomes. The most consistently
same. The Tribe 2012 trial also kept the time interval the same be- reported secondary outcomes were time from induction to delivery
tween incremental increases in dose, and compared pulsatile deliv- (five studies), hyperstimulation with fetal heart rate changes not
ery (low dose) with continuous delivery (high dose). Orhue 1993 specified (five studies), and postpartum haemorrhage (five studies).
kept the initial and incremental doses the same between groups No other secondary outcome was reported by more than three
but varied the time between incremental doses. studies. As some studies included women for either induction or
augmentation, or of mixed parity, results were not always presented
in a way that made it possible to include them in this analysis.
Inclusion criteria
The inclusion criteria also varied between the included trials.
Crane 1993 (abstract only), Hourvitz 1996, and Satin 1991 in- Excluded studies
cluded women who required induction of labour, and did not We excluded 30 studies from this review for one or more reasons
state any further inclusion or exclusion criteria. Lowensohn 1990 listed below. The majority of these were excluded for not having
(abstract only) and Dunn 1998 included women at greater than a high-dose arm or not having a low-dose arm as defined by the
37 weeks of gestation who needed induction of labour without review protocol.
further stating what indications for induction were included or ex- • In 11 of the excluded studies (Auner 1993; Blakemore
cluded. Willcourt 1994 included women with “adequate” pelvime- 1990; Cummiskey 1990; Daniel-Spiegel 2004; Fitzpatrick 2012;
try, no more than one prior caesarean section, and at least one Goni 1995; Lazor 1993; Mercer 1991; Muller 1992; Odem
of mild pregnancy-induced hypertension, diabetes, or postdates. 1988; Reid 1995), both groups were given a low-dose protocol
Women were excluded from final analysis if they needed magne- according to the review’s definitions.
sium sulphate, diabetes requiring insulin, or if they failed to estab- • In 11 of the excluded studies (Chua 1991; Durodola 2005;
lish within 24 hours. Merrill 1999 included all women at greater Gungorduk 2011; Manjula 2014; Orhue 1993b; Orhue 1994;
than 24 weeks’ gestation who required Induction or augmentation Parashi 2005; Ross 1998; Satin 1994; Steer 1985; Ustunyurt
of labour, however, their final results revealed a mean gestation of 2007), both groups were given a high-dose protocol according to
38.0 weeks with a standard deviation (SD) of 0.1, suggesting there the review’s definitions.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 10
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 • Seven of the excluded studies used the same dose in each • In one study (Compitak 2002), a mixed group of women
arm. In four trials (Daniel-Spiegel 2004; Diven 2012; Girard who needed induction or augmentation of labour were included,
2009; Ustunyurt 2007), the oxytocin infusion was stopped in and the study did not report outcomes based on induction of
one group at a pre-specified point in the induction; in labour versus augmentation of labour (and did not define
Gungorduk 2011 the groups differed in the time oxytocin was augmentation versus induction).
administered post cervical ripening; in Oral 2003 the groups • In one study (Parpas 1995), women were administered
were administered oxytocin in different mediums (saline versus a oxytocin based on maternal weight (not low versus high dose).
glucose solution); and in Pavlou 1978 groups were administered
oxytocin by different delivery systems (continuous versus pulsed). Risk of bias in included studies
• Three studies (Gibb 1985; Li 1996; Satin 1994) allocated
women to the two groups in a non-random fashion. Overall, the included trials were judged to be at a moderate to high
• In one study (Auner 1993), women who were all preterm risk of bias (see Figure 2 and Figure 3), with the risk of bias in many
were included. of the domains judged as ’unclear’, and insufficient information
available to permit confident judgements.

Figure 2. ’Risk of bias’ graph: review authors’ judgements about each risk of bias item presented as
percentages across all included studies.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 11
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Figure 3. ’Risk of bias’ summary: review authors’ judgements about each risk of bias item for each included
study.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 12
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Allocation
a high risk of attrition bias (Hourvitz 1996; Satin 1991; Willcourt
Four of the included trials had adequate methods for generat- 1994), due to unbalanced losses/exclusions without clear reason
ing a random sequence; three trials used random number ta- (Satin 1991) and due to not reporting the groups from which ex-
bles (Dunn 1998; Merrill 1999; Orhue 1993), and two trials cluded women were originally randomised (Willcourt 1994).
used computer-generated random number sequences (Tribe 2012;
Willcourt 1994). Two of these trials additionally used adequate
methods to conceal allocation (Merrill 1999; Orhue 1993), while Selective reporting
for the other two trials, the risk of selection bias due to inadequate Dunn 1998 and Tribe 2012 were the only included studies with a
concealment of allocation was unclear (Tribe 2012; Willcourt low risk of reporting bias, reporting on the pre-specified outcomes
1994). In two further trials (Lowensohn 1990; Satin 1991) the from its trial registration. While three trials (Hourvitz 1996; Orhue
risk of selection bias was unclear, due to non-reporting (or unclear) 1993; Satin 1991) reported on their outcomes specified in their
reporting of methods for sequence generation and allocation con- manuscript methods, with no access to the trial protocols, it was
cealment. The final two trials were quasi-randomised (with allo- not possible to confidently assess reporting bias. Two trials were
cation based on hospital number (Crane 1993) or based on time judged at an unclear risk of reporting bias, being presented in
period in the delivery ward (alternation of the protocol every two abstract form only (Crane 1993; Lowensohn 1990). The final two
months) (Hourvitz 1996)) and were thus judged to be at a high trials (Merrill 1999; Willcourt 1994) were judged at a high risk
risk of selection bias. of reporting bias, with unclear or no pre-specified outcomes of
interest detailed.
Blinding
Effective blinding of women and study personnel was unclear in Other potential sources of bias
the majority of trials (Crane 1993; Lowensohn 1990; Orhue 1993; In five of the included trials (Dunn 1998; Orhue 1993; Satin 1991;
Satin 1991; Willcourt 1994), with insufficient detail reported to Tribe 2012; Willcourt 1994) there were no other obvious poten-
make confident judgements. In three trials the risk of performance tial sources of bias identified. Compared to the results of other
bias due to ineffective blinding of women/study personnel was studies, Merrill 1999 has reported very narrow confidence inter-
judged to be high (due to the nature of the interventions) (Dunn vals suggesting measurement bias. For the other three included
1998; Hourvitz 1996; Tribe 2012). In only one trial (Merrill 1999) trials (Crane 1993; Hourvitz 1996; Lowensohn 1990), the risk of
was the risk of performance bias judged to be low - with adequate other bias was judged to be unclear, with insufficient information
blinding of women and personnel through the use of identical available to make this judgement confidently.
infusion bags and infusion rates (and rather use of differing con-
centrations in the infusion bags).
Effects of interventions
In eight of the nine trials, the risk of detection bias was judged to
be unclear (largely with inadequate detail provided for the review
authors to make confident judgements) (Crane 1993; Dunn 1998;
Hourvitz 1996; Lowensohn 1990; Orhue 1993; Satin 1991; Tribe High-dose versus low-dose oxytocin
2012; Willcourt 1994). In one trial however, detection bias was
judged to be low, with blinded outcome assessment, and the tri-
Primary outcomes
alists blinded until all outcomes were assessed (Merrill 1999).

Incomplete outcome data Vaginal delivery not achieved within 24 hours

The risk of attrition bias was judged to be low in the three of the Only two trials reported data on vaginal delivery not achieved
nine studies (Dunn 1998; Merrill 1999; Tribe 2012), where a high within 24 hours that could be included in the meta-analysis. Tribe
percentage of women were accounted for in each group and anal- 2012 reported specifically on vaginal delivery not achieved within
yses based on intention-to-treat principles. The risk of attrition 24 hours, while Merrill 1999 reported on women with ’failed in-
bias was judged as unclear in three of the studies (Crane 1993; duction’ (after oxytocin was given for eight to 12 hours without
Lowensohn 1990; Orhue 1993), where all women were accounted any progress in the induction process). Overall, there was no sig-
for but there was no detail provided as to whether there was any nificant difference between the high-dose and low-dose oxytocin
cross-over in the trial and if outcomes were analysed using inten- groups for this outcome (risk ratio (RR) 0.94, 95% confidence
tion-to-treat principles. The final three trials were judged to be at interval (CI) 0.78 to 1.14, two trials, 1339 women; Chi² = 0.03,

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 13
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
df = 1 (P = 0.85); I² = 0%) (Analysis 1.1). Excluding Merrill 1999 Time from induction to delivery
from this analysis due to high risk of bias does not change the When the five studies (Crane 1993; Hourvitz 1996; Merrill 1999;
estimate of effect. Tribe 2012; Willcourt 1994) that included these data are com-
bined, there is no significant difference between high- and low-
dose protocols (MD -0.90 hours, 95% CI -2.28 to + 0.49 hours;
Uterine hyperstimulation with fetal heart rate changes
five studies, 1725 women, Tau² = 2.27; Chi² = 93.34, df = 4 (P
None of the included studies reported specifically on the number < 0.00001, I² = 96% ) (Analysis 1.5). This represents substan-
of women who experienced uterine hyperstimulation with fetal tial heterogeneity and may result from any number of systematic
heart rate changes. problems with included studies. Specific issues are raised with the
standard deviations provided by Merrill 1999 being too small to be
realistic, Hourvitz 1996 excluding patients for analysis as they had
Caesarean section not received six hours of oxytocin and not reporting an intention-
This was the most consistently reported of our pre-specified pri- to-treat, and finally Willcourt 1994 who removed 40 patients for
mary outcomes (reported by eight of the nine included studies). failure to establish labour but did not include them in the analysis.
On meta-analysis, the risk of caesarean section was not significantly In addition to the issues outlined with the studies above, Dunn
different between the high-dose and low-dose oxytocin groups (RR 1998, Lowensohn 1990, Orhue 1993, and Satin 1991 did not
0.96, 95% CI 0.81 to 1.14; eight studies, 2023 women, Chi² = report data in a way that allowed it to be included in the meta-
9.70, df = 7 (P = 0.21); I² = 28%) (Analysis 1.2). When sensitivity analysis. These four trials reported a shorter induction to delivery
analysis is performed there are only two studies that are included times with high-dose protocol.
which still show no significant difference in caesarean section be- When sensitivity analysis is performed, Tribe 2012 is the only pa-
tween high- and low-dose groups (RR 1.01, 95% CI 0.81 to 1.25, per not excluded due to high risk of bias. They report a significant
two studies, 611 women, Chi² = 0.79, df = 2 (P = 0.32); I² = 0%). reduction in induction to delivery interval (MD -1.94 hours, 95%
(Analysis 5.1) CI -0.99 to -2.89 hours, 489 women) (Analysis 5.2).

Serious neonatal morbidity or death Uterine hyperstimulation (fetal heart rate changes not
Merrill 1999 was the only trial to report on serious neonatal mor- specified)
bidity/death, and found no significant difference between groups None of the authors in the included studies specified the rates
in a composite outcome of serious neonatal morbidity or death of uterine hyperstimulation without fetal heart rate changes, our
(RR 0.84, 95% CI 0.23 to 3.12, 781 infants) (Analysis 1.3). The prespecified secondary outcome. As five trials reported on uterine
inclusion criteria for this study included only singletons and were hyperstimulation, fetal heart rate changes not specified, we have
excluded if induction was for fetal death or abnormality. Therefore added the posthoc outcome “Uterine hyperstimulation, fetal heart
it is unclear why the authors have not reported on all infants and rate changes not specified”. This revealed a statistically significant
why there are more missing from the high-dose group than low- increase in hyperstimulation (fetal heart rate changes not specified)
dose group. for women receiving high-dose oxytocin compared with low-dose
oxytocin (RR 1.86, 95% CI 1.55 to 2.25; five trials, 876 women,
Chi² = 5.32, df = 4 (P = 0.26); I² = 25%) (Analysis 1.6).
Serious maternal morbidity or death When a sensitivity analysis was conducted to exclude the three
Tribe 2012 was the only study to report on serious maternal mor- trials at high risk of bias (Crane 1993; Lowensohn 1990; Satin
bidity or death, and found no significant difference between the 1991), the increased risk of hyperstimulation (fetal heart rate not
high-dose and low-dose groups for this outcome (RR 1.24, 95% specified) in the high-dose group was maintained (RR 1.92, 95%
CI 0.55 to 2.82, 523 women) (Analysis 1.4). CI 1.51 to 2.46; two studies, 611 women, Chi² = 3.07, df = 1
(P = 0.08); I² = 67%) (Analysis 5.3). This result is significantly
heterogenous however and is likely the result of the Orhue 1993
Secondary outcomes trial concentrating on grand multiparous women.
The reported complications of induction of labour with oxytocin
varied across the included studies. Time from induction to deliv-
ery and rates of hyperstimulation were the most commonly re- Uterine rupture
ported of our pre-specified secondary outcomes, however uterine Overall, there was no significant difference in the risk of rupture
rupture, epidural use, instrumental delivery, Apgar score, postpar- between the high-dose and low-dose oxytocin groups (RR 3.10,
tum haemorrhage, and endometritis were all reported on by at 95% CI 0.50 to 19.33; three trials, 1429 women, Chi² = 0.95, df
least two of the included trials. = 1 (P = 0.33); I² = 0%) (Analysis 1.7). It was noted that in the

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 14
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Orhue 1993 trial, three ruptures occurred in the high-dose group Postpartum haemorrhage
and no ruptures in the low-dose group. This trial assessed only Five of the nine included trials reported on rates of postpartum
women of high parity, which is important to consider. No uterine haemorrhage (Hourvitz 1996; Merrill 1999; Orhue 1993; Satin
ruptures occurred in Tribe 2012, and in Merrill 1999, there was 1991; Tribe 2012) and together, found no significant difference in
one rupture in each group. risk of postpartum haemorrhage for women receiving high-dose
versus low-dose oxytocin (RR 1.08, 95% CI 0.87 to 1.34; five
trials, 1600 women, Chi² = 3.53, df = 3 (P = 0.32); I² = 15%)
Epidural analgesia (Analysis 1.12).

Two trials reported on the use of epidural analgesia (Merrill 1999;

Tribe 2012), and on meta-analysis no significant difference was Endometritis
shown in the risk of having an epidural between the high-dose and
No significant difference in the risk of endometritis was shown
low-dose oxytocin groups (RR 1.03, 95% CI 0.89 to 1.19; two
between the high-dose and low-dose oxytocin groups across three
trials, 1327 women, Tau² = 0.01; Chi² = 3.80, df = 1 (P = 0.05); I² =
trials (Hourvitz 1996; Merrill 1999; Tribe 2012) (RR 1.35, 95%
74%) (Analysis 1.8). There was substantial statistical heterogeneity
CI 0.53 to 3.43; three trials, 1425 women, Tau² = 0.25; Chi² =
observed for this outcome, which may reflect the difference in the
3.14, df = 2 (P = 0.21); I² = 36%) (Analysis 1.13). There was
management of obstetric analgesia between the UK and USA or
moderate statistical heterogeneity observed between trials for this
the high risk of bias in the Merrill 1999 study. When this study is
outcome. Differences in the modes of delivery between studies,
removed, the single study by Tribe 2012 remains non-significant
time of follow-up and reporting of symptoms, and definition of
but the effect approaches a significant risk of epidural analgesia
endometritis likely account for much of this observed heterogene-
with high-dose oxytocin (RR 1.11, 95% CI 0.99 to 1.24).
ity.

Instrumental birth Other secondary outcomes

Three trials (Orhue 1993; Satin 1991; Tribe 2012) reported on None of the included trials reported on the other secondary re-
instrumental delivery, and showed no significant difference in the view outcomes, including: unchanged/unfavourable cervix after
risk between the high-dose and low-dose oxytocin groups (RR 12 to 24 hours, meconium-stained liquor, neonatal intensive care
1.22, 95% CI 0.89 to 1.66; three trials, 693 women, Chi² = 0.40, unit admission, neonatal encephalopathy, disability in childhood,
df = 2 (P = 0.82); I² = 0%) (Analysis 1.9). other maternal side-effects (nausea, vomiting, diarrhoea), mater-
nal antibiotic use, maternal satisfaction, neonatal infection and
neonatal antibiotic use.

Apgar score less than seven at five minutes

Subgroup analyses
No significant difference in the risk of an Agpar score less than
seven at five minutes was shown for infants born to mothers in the We performed subgroup analysis on the three predefined sub-
high-dose and low-dose oxytocin groups (RR 1.25, 95% CI 0.77 groups for whom subgroup data were available: previous cae-
to 2.01, five trials, 1641 infants, Chi² = 2.45, df = 4 (P = 0.65); I² sarean section or not, nulliparity or parity, and cervix unfavourable,
= 0%) (Analysis 1.10). favourable, or undefined. Subgroup analyses where membranes
are ruptured or not will be carried out in future updates of this
review as more data become available.

Perinatal death
There was no significant difference in perinatal death between the Previous caesarean section or not
high- and low-dose groups (RR 0.84, 95% CI 0.23 to 3.12; two Merrill 1999 provided data on women who had “unscarred uteri”
trials, 1302 women, unable to test for heterogeneity as there were for the outcome of caesarean section but not those with “scarred
no events in Tribe 2012). Merrill 1999 reported nine neonatal uteri” or for any of our other pre-specified primary outcomes. No
deaths (four infants born to mothers in the high-dose group, and other trials reported on a subgroup of women who had previously
five infants born to mothers in the low-dose group) (Analysis had a caesarean section. For women with “unscarred uteri”, there
1.11). These deaths were secondary to severe anomalies, karyotypic was no significant difference between high-dose and low-dose oxy-
abnormalities, or severe prematurity and were not attributed to tocin groups for the outcome caesarean section (RR 0.75, 95% CI
the intervention. 0.50 to 1.14, 720 women) (Analysis 2.1).

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 15
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Nulliparity or parity in the pre-specified primary outcomes of serious neonatal mor-
We performed subgroup analyses based on parity, including data bidity or death, or serious maternal morbidity and death, or in
from five of the included trials (Lowensohn 1990; Merrill 1999; any of the secondary adverse outcomes apart from hyperstimula-
Orhue 1993; Satin 1991; Willcourt 1994). Subgroup data were tion, between the regimens. Most trials did not report composite
available for the outcome of caesarean section from four trials. As outcomes that might have allowed effects on these individually
in the main analysis, no significant difference between high-dose uncommon outcomes to be demonstrated.
and low-dose oxytocin groups was observed in the nulliparous or
multiparous subgroups for the outcome caesarean section, and no
significant subgroup interaction was identified for this outcome
(Chi² = 3.25, P = 0.07, I² = 69.2%) (Analysis 3.2). Similarly, as in Overall completeness and applicability of
the main analysis, an increase in hyperstimulation was observed evidence
for women in the high-dose oxytocin group for both the nulli- There is currently a wide variation amongst clinicians about what
parous and multiparous subgroups; however, no significant sub- constitutes high-dose and low-dose oxytocin infusion regimens for
group interaction was identified for this outcome, indicating no induction of labour. This variation is complicated by how often
differential effect based on parity for the outcome hyperstimula- oxytocin is increased, whether the dose increment is linear or non-
tion (Chi² = 0.16, P = 0.69, I² = 0%) (Analysis 3.1). linear, and if the infusion is delivered continuously or in a pulsed
fashion. As a result of this variation we constructed a high- and low-
dose definition based on the half life of oxytocin for the purpose
Cervix unfavourable, favourable, or undefined
of this review. Because of the heterogeneity in oxytocin regimens
Willcourt 1994 reported on the rates of caesarean section based in existing clinical trials, most screened studies did not meet our
on a cervical dilation of less than or more than 5 cm at the time of inclusion criteria, meaning there are considerable data available on
induction of labour. There was no significant difference between this topic that is not further analysed in this review. A particular
the high-dose versus low-dose groups in the risk of caesarean sec- problem was reporting on rates of hyperstimulation by included
tion for either of the subgroups (as in the main analysis), and no studies without specifying the effect on fetal heart rate, and impact
significant subgroup interaction was identified for this outcome on subsequent management such as a change in oxytocin infusion
(Chi² = 0.06, P = 0.80, I² = 0%) (Analysis 4.1), indicating no dif- rates. Lowensohn 1990 discussed that many women may not have
ferential effect for this outcome based on favourable/unfavourable actually have received the high dose they were allocated due to the
cervix at time of induction. No trials reported on any of our other rates of hyperstimulation but have not analysed this further, and
pre-specified primary outcomes according to cervical status. this has not been reported by other studies. It is unclear whether
this was a finding confined to that particular study, or whether
other authors may not have considered this factor in their data
analysis.
DISCUSSION Regarding the setting of the included studies, all except Orhue
1993 were completed in tertiary centres in high-income countries.
Orhue 1993 was undertaken at a tertiary centre in a low-income
country. Depending on the intrapartum monitoring and back-
Summary of main results up medical and surgical services available, the outcome of this
We have included nine trials, involving 2391 women and their Cochrane review may be less relevant to peripheral health facilities,
babies in this review. None of the included studies reported specif- particularly those in low-income countries.
ically on this review’s primary outcome (the number of women The differing demographics of the patient populations under
who experienced uterine hyperstimulation with fetal heart rate study, with insufficient included patients for meaningful subgroup
changes).The only consistently reported pre-specified primary analysis by parity or previous mode of birth, also limits the con-
outcome amongst included studies was caesarean section rate, clusions that can be drawn from the meta-analysis. In particular,
which was similar between groups. When only studies without Orhue 1993’s high-parity population is unlikely to be representa-
high risk of bias were analysed, the high-dose protocol may reduce tive of a general cohort of multiparous women undergoing oxy-
the induction to delivery interval; however, when data from all the tocin induction. The 7% rate of uterine rupture in this study is
included studies are pooled for this outcome, there is no significant clearly of concern, and suggests high-dose oxytocin regimens are
difference seen in induction to delivery interval between high-dose likely unsuitable for women of high parity, however this finding
and low-dose protocols. A significantly increased rate of uterine cannot be generalised to the nulliparous or low parity population.
hyperstimulation, with its potential for increased adverse neonatal No trials reported on maternal satisfaction or caregiver satisfaction,
and maternal outcomes, was found with use of the high-dose pro- so evidence is lacking about this important aspect of the induction
tocol. However, there were no significant differences found either process.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 16
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Quality of the evidence labour without increasing the rate of caesarean section. They also
have concluded there is an increase rate of hyperstimulation but
Included studies were mostly of small size and only moderate qual-
there is not expansion on the effect of this hyperstimulation to
ity. Undertaking a sensitivity analysis of the studies to include
mother or baby.
only those with low risk of bias changed the findings regarding in-
Finally, when augmentation rather than induction is considered,
duction to delivery interval from a non-significant reduction with
Kenyon et all (Kenyon 2011) concluded that high-dose oxytocin
high-dose protocol (all included studies) to a significant reduc-
regimens were associated with a reduction in the length of labour
tion (low risk of bias studies). For the other two outcomes where
and in caesarean section, and an increase in spontaneous vaginal
data existed to perform sensitivity analysis, caesarean section and
delivery.
uterine hyperstimulation (fetal heart rate changes not specified),
there was minimal difference in findings when only low risk of bias
studies were included. With the exception of Tribe 2012, studies
were performed at least 15 years prior to this review and two were
published in abstract form only, limiting both the ability to ob- AUTHORS’ CONCLUSIONS
tain additional data from the included studies for this review and
attempts to clarify the details of existing data. Implications for practice
We have not found evidence that using high-dose oxytocin in-
Potential biases in the review process creases vaginal delivery or the rate of caesarean section. However,
there is some evidence that using high-dose oxytocin increases the
Our prespecified decision (made at the time of writing the pro- risk of uterine hyperstimulation (fetal heart rate changes not spec-
tocol for this review) to set absolute cut-offs for what cumulative ified). It also has not been shown to have any clear benefit in any
oxytocin dose would be considered a high-dose regimen versus a other measured outcomes for the studies that we were able to in-
low-dose regimen, potentially introduces study selection bias into clude in this review, in particular, no significant reduced induc-
the review. This decision was made as a number of studies in this tion to delivery time was found on meta-analysis. We did not find
area label as “low-dose” oxytocin regimens that for other authors evidence of an increased risk of other adverse outcomes that have
were “high dose”, and it was therefore felt study inclusion in this been measured in studies thus far.
review based solely on original study authors’ definitions of “low
dose” and “high dose” would lead to uninterpretable meta-analysis The numbers of women and babies included in this review may
findings. However, in a future review we may include alternative have been too small to show a difference in some more rare out-
definitions and analysis (e.g. very low dose, low dose, intermediate comes such as neonatal infection, maternal symptoms, and pla-
dose, high dose) to allow for greater inclusion of original study cental abruption. Currently however, there is no evidence to sup-
data. port the use of high-dose oxytocin for the induction of labour.
The decision to include only studies of induction of labour at
term, rather than at anytime during the third trimester, is also Implications for research
a potential bias. As only one study was found in the trial search Further research in this area would need to be focused on several
where this was the reason for trial exclusion, we do not feel that outcomes that include induction to delivery time, impact of uter-
this is likely to have had a major impact. An alternative for future ine hyperstimulation (with and without fetal heart rate changes),
reviews would be to include all studies regardless of gestation, and maternal and neonatal morbidity, maternal and caregiver satisfac-
perform subgroup analysis according to whether the induction of tion, and hospital stay. Further research should also aim for a better
labour was at term or preterm. understanding about the most effective delivery method (pulsed
versus continuous) and the rate at which oxytocin should be in-
creased.
Agreements and disagreements with other
studies or reviews
The findings of this review in the outcomes of caesarean section are
similar to those found by Pakta 2005. In addition, these authors
ACKNOWLEDGEMENTS
found there was a decreased Induction to delivery interval in their
review. In contrast to this review however, they have set limited We wish to thank Dr Rachel Tribe for providing additional out-
parameters on what is defined as high- and low-dose. come data relating to the Tribe 2012 publication to be included
In their review of Oxytocin in 2006, Smith and Merrill (Smith in this review. We also wish to thank Prof AAE Orhue and Dr
2006) concluded that both high- and low-dose oxytocin protocol J Crane for clarifying details relating to Orhue 1993 and Crane
appeared safe but a high dose appeared to shorten the length of 1993 respectively.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 17
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Thank you to Phillipa Middleton and Emer Heatley for their
advice in the development of the protocol and how to conduct
and write the protocol and the subsequently the review.
As part of the pre-publication editorial process, this review has
been commented on by three peers (an editor and two referees
who are external to the editorial team), members of the Pregnancy
and Childbirth Group’s international panel of consumers and the
Group’s Statistical Adviser.

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Lazor LZ, Philipson EH, Ingardia CJ, Kobetitsch ES, Curry
Daniel-Spiegel 2004 {published data only} SL. A randomized comparison of 15- and 40-minute dosing
Daniel-Spiegel E, Weiner Z, Ben-Shlomo I, Shalev E. For protocols for labor augmentation and induction. Obstetrics
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Li F, Liu C. Clinical study on induction of labor with
Diven 2012 {published data only} feedback pulsatile oxytocin system. Chung-Hua Fu Chan
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Quinones JN. Oxytocin discontinuation during active labor An International Journal of Obstetrics and Gynaecology 2014;
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Mercer 1991 {published data only}
Durodola 2005 {published data only} Mercer B, Pilgrim P, Sibai B. Labour induction with
Durodola A, Kuti O, Orji EO, Ogunniyi SO. Rate of continuous low-dose oxytocin infusion: a randomised trial.
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International Journal of Gynecology and Obstetrics 2005;90 Muller 1992 {published data only}
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Fitzpatrick 2012 {published data only} randomized clinical trial comparing two oxytocin induction
Fitzpatrick CB, Grotegut CA, Bishop TS, Canzoneri protocols. American Journal of Obstetrics and Gynecology
BJ, Heine RP, Swamy GK. Cervical ripening with foley 1992;167:373–81.
balloon plus fixed versus incremental low-dose oxytocin: A Odem 1988 {published data only}
randomized controlled trial. Journal of Maternal-Fetal and Odem RR, Work BA, Dawood MY. Pulsatile oxytocin for
Neonatal Medicine 2012;25(7):1006–10. induction of labor: a randomized prospective controlled
study. Journal of Perinatal Medicine 1988;16:31–7.
Gibb 1985 {published data only}
Arulkumaran S, Gibb DMF, Ratnam SS, Lun KC, Heng Oral 2003 {published data only}
SH. Total uterine activity in induced labour - an index Oral E, Gezer A, Cagdas A, Pakkal N. Oxytocin infusion
of cervical and pelvic tissue resistance. British Journal of in labor: the effect different indications and the use of
Obstetrics and Gynaecology 1985;92:693–7. different diluents on neonatal bilirubin levels. Archives of
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Gibb DMF, Arulkumaran S, Ratnam SS. A comparative Gynecology and Obstetrics 2003;267:117–20.
study of methods of oxytocin administration for induction Orhue 1993b {published data only}
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Girard 2009 {published data only} women of low parity. International Journal of Obstetrics and
Girard B, Vardon D, Creveuil C, Herlicoviez M, Dreyfus Gynaecology 1993;40:219–25.
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Goni 1995 {published data only} a randomized controlled trial. Obstetrics and Gynecology
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labor: a comparison of 20- and 60-min dose increment Parashi 2005 {published data only}
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(6):540. Salamalekis E, Vitoratos N, Kassanos D, Loghis C,
Parpas 1995 {published data only} Panayotopoulos N, Sykiotis C. A randomized trial
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JC. Randomised trial of 2 dosages of oxytocin for labour induction. Clinical and Experimental Obstetrics and
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(syntocinon) dans le declenchement ou la direction du Singh 1993 {published data only}
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Gynecologie, Obstetrique et Biologie de la Reproduction 1995; oxytocin for induction of labour. Proceedings of 49th
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Pavlou C, Barker GH, Roberts A, Chamberlain GVP. Pulsed Ontario, Canada. 1993:48.
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Rang 2007 Toaff 1978
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High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 21
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
CHARACTERISTICS OF STUDIES

Characteristics of included studies [ordered by study ID]

Crane 1993

Methods Quasi-randomised controlled trial.

Participants 130 women requiring induction of labour. 61 randomised to high-dose group and 69
randomised to low-dose group

Interventions High-dose group: oxytocin started at 7 mU/min, increased by 7 mU/min at 15-min

intervals to a maximum of 40 mU/min
Low-dose group: oxytocin started at 1.4 mU/min, increased by 1.4 mU/min at 30-min
intervals to a maximum of 20 mU/min

Outcomes Time to delivery (primary outcome). Mode of delivery, maternal and neonatal morbidity
(secondary outcomes)

Notes Performed in a tertiary hospital in New Brunswick, Canada - the largest single health
facility in the province. Author contacted, women at term, no further information avail-
able owing to length of time from original study (records destroyed). Abstract only

Risk of bias Risk of bias

Bias Authors’ judgement Support for judgement

Random sequence generation (selection High risk Participants were randomised by hospital number
bias) potentially allowing researchers to predict in ad-
vance which protocol a patient would receive

Allocation concealment (selection bias) High risk Study was quasi-randomised.

Blinding of participants and personnel Unclear risk Not stated.

(performance bias)
All outcomes

Blinding of outcome assessment (detection Unclear risk Not stated.

bias)
All outcomes

Incomplete outcome data (attrition bias) Unclear risk All patients were accounted for in the outcomes
All outcomes that were reported. No patients appear to have
been excluded after randomisation. There was no
explicit reporting of an intention-to-treat but the
numbers in the reported outcomes are concurrent
with the number in allocated to each group

Selective reporting (reporting bias) Unclear risk Not enough information provided to determine.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 22
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Crane 1993 (Continued)

Other bias Unclear risk Not enough information provided to determine.

Dunn 1998

Methods Randomised, prospective trial using sealed opaque envelopes and a random number table

Participants 128 women with singleton pregnancy ≥ 37 weeks who required induction of labour.
Women were excluded if they had multiple gestation, known chorioamnionitis, prema-
turity, EFW > 4000 g, non-vertex presentation, or uterine scar

Interventions High-dose group: oxytocin started at 2 mU/min and increased every 15-20 mins, initially
doubled to 4 mU then increased by 4 mU on each increment there after
Low-dose group: oxytocin started at 0.5-1mU/min and increased by 1-2 mU/min at 30-
min intervals

Outcomes Primary outcomes included time from induction to delivery and incidence of umbilical
cord pH < 7.20. Secondary outcomes included maternal pain, incidence of caesarean
delivery, maternal fever, Apgar < 7 at 1 min, Apgar < 7 at 5 minutes, incidence of non-
reassuring FHR changes, and incidence of uterine hyperstimulation. Failed induction
was also recorded but not a pre-specified outcome

Notes Doctoral thesis.

Risk of bias Risk of bias

Bias Authors’ judgement Support for judgement

Random sequence generation (selection Low risk Random number table generated and allo-
bias) cation placed in numbered opaque sealed
envelopes

Allocation concealment (selection bias) High risk No concealment. Dose was different be-
tween groups.

Blinding of participants and personnel High risk There was no blinding of the staff or pa-
(performance bias) tient.
All outcomes

Blinding of outcome assessment (detection Unclear risk Not stated.

bias)
All outcomes

Incomplete outcome data (attrition bias) Low risk All pre-specified outcomes were reported.
All outcomes

Selective reporting (reporting bias) Low risk Study protocols were adhered to with re-
porting of all pre-specified outcomes

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 23
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Dunn 1998 (Continued)

Other bias Low risk None identified.

Hourvitz 1996

Methods Quasi-randomised controlled trial.

Participants 211 women at term requiring induction of labour. 113 randomised to high-dose group
and 98 randomised to low-dose group

Interventions High-dose group: oxytocin started at 2.5 mU/min, increased by 2.5 mU/min at 30-min
intervals till 30 mU/min, then 5 mU/min increments to a maximum dose of 30 mU/
min
Low-dose group: oxytocin started at 1.25 mU/min, increased by 1.25 mU/min at 30
min intervals till 7.5 mU/min then 2.5 mU/min increments till of 15 mU/min, then 5
mU/min to a maximum of 30 mU/min

Outcomes Primary outcomes included time from induction to delivery, maximal oxytocin dose,
number of times infusion was stopped or decreased for hyperstimulation of suspicious
FHR changes, and use of anaesthetic. Secondary outcomes include methods of delivery,
PPH, endometritis, cervical tears, length of hospital stay, Agpar scores, birthweight

Notes Undertaken at the Chaim Sheba Medical Centre - tertiary and largest hospital in Israel
Failed induction of labour was defined as women not in active labour after 6 hours but
they have not mentioned rates of failure at 24 hours

Risk of bias Risk of bias

Bias Authors’ judgement Support for judgement

Random sequence generation (selection High risk Randomisation was performed on a temporal ba-
bias) sis, alternating the protocol used in the delivery
ward every 2 months

Allocation concealment (selection bias) High risk No concealment.

Blinding of participants and personnel High risk Different infusion rates would be noticeable by
(performance bias) both participants and personnel
All outcomes

Blinding of outcome assessment (detection Unclear risk Not stated.

bias)
All outcomes

Incomplete outcome data (attrition bias) High risk 32 patients were excluded after randomisation as
All outcomes they had not received 6 hours of oxytocin. They
were not analysed with intention-to-treat

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 24
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Hourvitz 1996 (Continued)

Selective reporting (reporting bias) Unclear risk Pre-specifed outcomes were reported, however
with no access to a trial protocol it is not possible
to confidently assess selective reporting

Other bias Unclear risk Potential bias related to short duration of trialled
oxytocin before calling it a failed induction of
labour

Lowensohn 1990

Methods Randomised controlled trial.

Participants 104 women greater than or equal to 37 weeks’ gestation requiring Induction or augmen-
tation of labour. 55 of these women were induced. 25 women in the high-dose group
and 30 women in the low-dose group

Interventions High-dose group: oxytocin starting at 6.67 mU/min, increased by 6.67 mU/min every
15 mins to a maximum of 40 mU/min
Low-dose group: oxytocin started at 1 mU/min, increased every 30-40 mins to a maxi-
mum dose of 4 mU/min

Outcomes Time from induction to delivery, labour dystocia, recurrent hyperstimulation, failure to
achieve labour, fetal distress requiring caesarean delivery, vaginal delivery rate. Outcomes
were reported separately for induction and augmentation groups

Notes Undertaken at Oregon Health Sciences University Hospital - tertiary hospital and trauma
centre in Portland, USA
Abstract only. Attempted to contact authors however no reply was received

Risk of bias Risk of bias

Bias Authors’ judgement Support for judgement

Random sequence generation (selection Unclear risk No discussion of sequence generation.

bias)

Allocation concealment (selection bias) Unclear risk Not stated in abstract.

Blinding of participants and personnel Unclear risk Not stated.

(performance bias)
All outcomes

Blinding of outcome assessment (detection Unclear risk Not stated.

bias)
All outcomes

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 25
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Lowensohn 1990 (Continued)

Incomplete outcome data (attrition bias) Unclear risk Outcome data are only presented for 103 women, with
All outcomes no explanation of what occurred to 1 woman. There was
no discussion of exclusion after randomisation, inten-
tion-to-treat analysis, or dropouts

Selective reporting (reporting bias) Unclear risk Not enough information provided to determine.

Other bias Unclear risk Not enough information provided to determine.

Merrill 1999

Methods Double-blinded randomised controlled trial.

Participants 816 women for induction of labour and 491 women for augmentation of labour. Women
being induced had to be greater than 24 weeks’ gestation with a live fetus, be less than 3
cm dilated or have less than 10 contractions per hour. 404 women were randomised to
the high-dose group and 412 to the low-dose group

Interventions High-dose group: oxytocin starting at 4.5 mU/min, increased by 4.5 mU/min every 30
mins
Low-dose group: oxytocin starting at 1.5 mU/min and increased by 1.5 mU/min every
30 mins

Outcomes There were no pre-specified outcomes. Reported outcomes include numbers of caesarean
section, serious maternal morbidity or death, serious neonatal morbidity or perinatal
death, time from induction of labour to delivery, uterine hyperstimulation, uterine rup-
ture, epidural analgesia, Apgar less than 7 at 5 mins, PPH, chorioamnionitis, and en-
dometritis

Notes Undertaken at University of Iowa Hospitals and Clinics - only tertiary level hospital in
Iowa

Risk of bias Risk of bias

Bias Authors’ judgement Support for judgement

Random sequence generation (selection Low risk Random number tables located in the cen-
bias) tral pharmacy.

Allocation concealment (selection bias) Low risk Infusion bags were made in a central phar-
macy with a minimal difference in total vol-
ume. Infusion rates were the same between
groups

Blinding of participants and personnel Low risk The infusion rates were the same between
(performance bias) groups with only the concentration higher
All outcomes in 1 group. There was no distinguishable
difference in the preparations

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 26
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Merrill 1999 (Continued)

Blinding of outcome assessment (detection Low risk All data were entered before any codes bro-
bias) ken.
All outcomes

Incomplete outcome data (attrition bias) Low risk Only 1 patient lost to follow-up. Intention-
All outcomes to-treat analysis was evident in most of the
reported outcomes

Selective reporting (reporting bias) High risk There were no pre-specified outcomes. Au-
thors may have only reported some of their
findings

Other bias High risk Confidence intervals for statistical analysis

of outcomes much narrower than for other
studies, and more than would be expected
from the larger study size alone, raising con-
cerns about accuracy of the statistical anal-
ysis

Orhue 1993

Methods Randomised controlled trial.

Participants 90 women with 5 or more previous births who required an induction of labour. 44
women were randomised to the high-dose group and 46 women to the low-dose group

Interventions High-dose group: oxytocin starting at 2 mU/min, doubled every 15 mins to a maximum
of 32 mU/min or when 3 uterine contractions every 10 mins established
Low-dose group: oxytocin started at 2 mU/min, doubled every 45 mins to a maximum
dose of 32 mU/min or when 3 uterine contractions every 10 mins established

Outcomes Mode of delivery, complications of labour and delivery (uterine rupture, hyperstimula-
tion, PPH, perineal trauma, puerperal pyrexia), number of days in hospital

Notes Undertaken at University of Benin Teaching Hospital - tertiary hospital in Lagos

Author contacted April 2012 and confirmed that all participants were at term

Risk of bias Risk of bias

Bias Authors’ judgement Support for judgement

Random sequence generation (selection Low risk Randomised code from a table of random numbers.
bias)

Allocation concealment (selection bias) Low risk Numbered opaque sealed envelopes.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 27
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Orhue 1993 (Continued)

Blinding of participants and personnel Unclear risk This was not discussed in adequate detail. Given the
(performance bias) different rates of infusion blinding is unlikely
All outcomes

Blinding of outcome assessment (detection Unclear risk Not stated.

bias)
All outcomes

Incomplete outcome data (attrition bias) Unclear risk No patient loss to follow-up, no exclusion after randomi-
All outcomes sation, no dropouts. It is unclear if there was intention-
to-treat analysis

Selective reporting (reporting bias) Unclear risk All pre-determined outcomes were reported, however
with no access to a trial protocol it is not possible to
confidently assess selective reporting

Other bias Low risk No other obvious sources of bias identified.

Satin 1991

Methods Randomised controlled trial.

Participants 90 women admitted to labour and delivery suite for induction of labour. 10 excluded
women not included in analysis. 48 women were randomised to the high-dose group
and 32 women to the low-dose group, 10 women were not reported on

Interventions High-dose group: oxytocin starting at 2 mU/min, increased by 2 mU/min every 15 mins
(150 mU at 40 min, 1080 mU at 2 hours) 48 women
Low-dose group: oxytocin starting at 2 mU/min and increased by 1 mU/min every 30
mins (90 mU at 40 min, 420 mU at 2 hours). 32 women

Outcomes Frequency of operative deliveries, chorioamnionitis, endometritis, PPH, Apgar scores,

umbilical cord gas values, infection rate, and hospital stay

Notes Undertaken at Wilford Hall United States Air Force Medical Center - military hospital
10 women were excluded because they had hypertensive disease requiring magnesium
sulphate

Risk of bias Risk of bias

Bias Authors’ judgement Support for judgement

Random sequence generation (selection Unclear risk Not stated how the randomisation sequence was gener-
bias) ated.

Allocation concealment (selection bias) Unclear risk Allocation was based on unmarked, sealed envelopes.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 28
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Satin 1991 (Continued)

Blinding of participants and personnel Unclear risk Patients received monitoring in a similar fashion despite
(performance bias) allocation. Whilst it is not stated if the participants and
All outcomes personnel were blinded, it is unlikely given the time of
incremental increase

Blinding of outcome assessment (detection Unclear risk Not stated.

bias)
All outcomes

Incomplete outcome data (attrition bias) High risk 10 patients were excluded after randomisation with more
All outcomes removed in the low-dose group compared to the high-
dose group. These patients were not analysed with in-
tention-to-treat

Selective reporting (reporting bias) Unclear risk All primary pre-specified outcomes were reported, how-
ever with no access to a trial protocol it is not possible
to confidently assess selective reporting

Other bias Low risk No other obvious sources of bias identified.

Tribe 2012

Methods Unblinded parallel group randomised controlled trial. Block randomisation by hospital,
labour intervention required (augmentation versus induction of labour), and gestation
(37+ weeks versus < 37 weeks)

Participants Women 18 years+ requiring induction or augmentation of labour. 523 women requiring
induction of labour were included in the trial, only 11 of whom were less than 37 weeks’
gestation. Baseline characteristics were similar. 257 were randomised to the high-dose
group and 266 women randomised to the low-dose group

Interventions High-dose: oxytocin starting at 2 mU/min, doubling of infusion rate every 30 mins
Low-dose: oxytocin starting at 2 mU/pulse, pulsed every 6 mins, with doubling of pulse
dose every 30 mins until 3 or 4 uterine contractions in 10 mins established

Outcomes Primary: caesarean section rate.

Secondary: vaginal delivery not achieved within 24 hours, time from induction to de-
livery, pain relief, serious maternal morbidity or death, serious neonatal morbidity or
death, uterine hyperstimulation, meconium-stained liquor, PPH, fetal distress (clinical
judgement), need for fetal blood sampling, Apgar less than 7 at 5 mins, and NICU
admission

Notes Undertaken at 2 inner-city UK university tertiary hospitals.

Primary reference for Crawshaw 2008. Additional data supplied by Dr Tribe July 2012

Risk of bias Risk of bias

Bias Authors’ judgement Support for judgement

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 29
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Tribe 2012 (Continued)

Random sequence generation (selection Low risk Computer-generated allocation designed

bias) by a statistician.

Allocation concealment (selection bias) Unclear risk Participants were assigned a treatment
group by the computer after entry of base-
line data

Blinding of participants and personnel High risk Study was not blinded as the 2 infusion
(performance bias) pumps used for pulsatile and continuous
All outcomes infusions were visually distinct

Blinding of outcome assessment (detection Unclear risk It is not stated if outcome assessors were
bias) blinded.
All outcomes

Incomplete outcome data (attrition bias) Low risk No loss to follow-up during intervention.
All outcomes 15 women crossed over from pulsatile to
continuous, 2 women in pulsatile with-
drew consent for analysis. Intention-to-
treat analysis

Selective reporting (reporting bias) Low risk Trial pre-registered. All pre-specified out-
comes reported.

Other bias Low risk No other obvious sources of bias identified.

Willcourt 1994

Methods Randomised controlled trial.

Participants 358 women requiring induction of labour for post dates, gestational hypertension, or
diabetes. Data only recorded for 310 women. *7 women were randomised to the high-
dose group, 109 women to the continuous low-dose group, and 114 women the pulsed
(low-dose) group)

Interventions High-dose infusion: oxytocin starting at 0.67 mU/min, increased by 2 mU/min every
15 mins
Low-dose infusion: oxytocin starting at 0.67 mU/min, increased by 1 mU/min every 30
mins until uterine contractions were established
Pulsed infusion: 0.67 mU administered over 5 seconds every 5 mins over 40 mins,
increased to 2 mU administered over 5 seconds every 5 mins over 40 mins, and then
increased by 1 mU/pulse every 40 mins until labour established
Results were only compared between the pulsed group to each continuous group and
not between high and low continuous groups

Outcomes Induction to delivery time, caesarean section rates, cord lactic acid

Notes Undertaken at Kapiolani Medical Center for Women and Children

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 30
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Willcourt 1994 (Continued)

Risk of bias Risk of bias

Bias Authors’ judgement Support for judgement

Random sequence generation (selection Low risk Computer-generated, randomly assigned sequence.
bias)

Allocation concealment (selection bias) Unclear risk This is not described.

Blinding of participants and personnel Unclear risk Not stated.

(performance bias)
All outcomes

Blinding of outcome assessment (detection Unclear risk Not stated.

bias)
All outcomes

Incomplete outcome data (attrition bias) High risk 48 patients were removed after randomisation for wors-
All outcomes ening diabetes, hypertension requiring magnesium sul-
phate, or not labouring within 24 hours. It it not ex-
plained which group these women were assigned. No
intention-to-treat analysis

Selective reporting (reporting bias) High risk No pre-defined outcomes were reported. No collective
results reported, only subgroup analysis

Other bias Low risk No other obvious sources of bias identified.

EFW: estimated fetal weigh

FHR: fetal heart rate
mU: milli units
min(s): minutes
NICU: neonatal intensive care unit
PPH: postpartum haemorrhage

Characteristics of excluded studies [ordered by study ID]

Study Reason for exclusion

Auner 1993 This study includes women in the setting of premature rupture of membranes. The study assessed continuous
infusion (oxytocin 120 mU at 40 min, 540 mU at 2 hrs) versus pulsed at 10-min intervals (25 mU at 40
mins, 150 mU at 2 hrs) The study was excluded as the high-dose protocol did not reach 600 mU at 2 hrs and
it only involved women who were preterm

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 31
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
(Continued)

Blakemore 1990 Both groups started at 0.5 mU/min, and the study compared increases at 15 min (77.5 mU at 40 min, 817
mU at 2 hrs) versus 1 hr (20 mU at 40 min, 150 mU at 2 hrs). Whilst the study aimed to compare dose
schedules, both groups would be classified as low-dose by this protocol, as the control group did not reach
100 mU by 40 mins

Chua 1991 Both arms of the study described an oxytocin infusion regimen that was high-dose according to the review’s
pre-specified definition (Regimen 1: 125 mU by 40 mins, 750 mU by 120 mins, Regimen 2: 187.5 mU by
40 minutes, 1350 mU by 120 mins)

Compitak 2002 This study describes randomisation of women requiring both augmentation and induction of labour but has
not reported how they have defined these 2 groups. In reporting their results, they have not stratified their
findings by induction and augmentation

Cummiskey 1990 This study randomised women to pulsed or continuous infusion groups. The pulsed group received a total
oxytocin of 7 mU at 40 mins and 93 mU at 2 hrs whilst the continuous group received 50 mU at 40 mins
and 300 mU at 2 hrs. Therefore, both groups would be classified into low-dose by this protocol

Daniel-Spiegel 2004 This study compared continuation oxytocin infusion versus cessation of oxytocin at a cervical dilatation of 5
cm in women requiring induction of labour. Both groups used the same dose schedule until cervical dilatation
of 5 cm then oxytocin infusion was ceased for 1 group, whilst continued for the other group. The protocol
used by the authors would be in the low-dose category for both arms (60 mU at 40 mins, 420 mU at 2 hrs)

Diven 2012 This study compared the continuation versus cessation of oxytocin once active labour had been achieved in
women requiring induction of labour. Both groups used the same dose schedule until labour was established,
defined by cervical dilatation of greater than 4 cm, then oxytocin infusion was ceased for 1 group, whilst
continued for the other group. Oxytocin infusion regimens could not be differentiated

Durodola 2005 This study compared linear versus non-linear increases in oxytocin dose. In the arithmetic (linear) group,
women received total oxytocin dose of 160 mU at 40 mins and 1200 mU at 2 hrs, whilst women in the
geometric (non-liner) group received 160 mU at 40 mins and 1800 mU at 2 hrs. Therefore both groups
would be classified as high-dose by this protocol

Fitzpatrick 2012 This study was excluded as neither group reached high-dose oxytocin. The study compared women with a
fixed low-dose oxytocin versus their standard low-dose regimen after women had received Foley’s catheter
cervical ripening. In the fixed group, women received 80 mU at 40 min and 280 mU at 2 hrs versus the
standard group which received 50 mU at 40 min and 510 mU at 2 hrs

Gibb 1985 This study was not a randomised trial. 121 women were allocated to 1 of 2 methods of administration of the
infusion based on the availability of the equipment. The automatic infusion of oxytocin in a closed loop system
for the induction of labour was compared with manual administration of oxytocin by peristaltic infusion
pump

Girard 2009 This study examined the effects of continuous oxytocin versus cessation of oxytocin at the beginning of the
active phase of labour in women requiring induction of labour. Both groups received the same amount of
oxytocin until that point. The authors were not strict about the amount of initial oxytocin or the time when
it was increased. As the only difference is when oxytocin is ceased, we have excluded this trial

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 32
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
(Continued)

Goni 1995 This study compared the timing by which doses should be increased. The traditional protocol group received
a total of 60 mU at 40 mins and 1260 mU at 2 hrs whilst the low-dose group received 40 mU at 40 mins and
180 mU at 2 hrs. Therefore, both groups would be classified as low-dose by this protocol

Gungorduk 2011 This study compared high-dose oxytocin protocol with either concurrent administration of sustained-release
dinoprostone or delayed oxytocin by 6 hrs. Both groups received the same oxytocin and only differed by the
time post cervical ripening

Lazor 1993 This study compared timing of oxytocin increase and the amount they were raised by. The 15-min group
started at 1 mU/min and increased by 1 mU/min every 15 mins (total oxytocin dose at 40 mins of 75 mU
and 525 mU at 2 hrs) whilst the 40-min group started at 1 mU/min and increased by 1.5 mU/min every 40
mins (40 mU at 40 mins, 300 mU at 2 hrs). Therefore both groups would be classified as low-dose by this
protocol

Li 1996 Non-randomised study and exact dosages of oxytocin not available for 2 arms in translation of paper. Authors
contacted without reply

Manjula 2014 This study (abstract only) reported 200 women randomised to high- versus intermediate-dose oxytocin for
induction of labour at ≥37 weeks. Both groups however were in the higher dose category as defined by our
review group. The high-dose group received 240 mU at 40 minutes and 1320 at 2 hrs whilst the intermediate-
dose group received 120 mU of oxytocin at 40 minutes and 660 mU at 2 hrs

Mercer 1991 This study compared 2 non-linear protocols which varied only by time. The traditional protocol group received
total oxytocin of 30 mU at 40 mins and 490 mU at 2 hrs whilst the low-dose group received 20 mU at 40
mins and 90 mU at 2 hrs. The timing of amniotomy was also different between the two groups, the traditional
protocol receiving amniotomy as soon as a Amnihook could be passed and the low-dose only when the Bishops
score was greater than 6. While both groups would be classified into low-dose by this protocol, the timing of
amniotomy does not allow adequate comparison for this protocol

Muller 1992 This study compared 2 groups using different time intervals as well as comparing linear and non-linear
increases in oxytocin infusion. Furthermore, the protocol for this study allows for a variable dose starting
within each group, effecting the non-linear groups rates of infusion, whilst the linear group also had variable
dose increases between group members. From the protocol, the traditional group would receive 40-100 mU
at 40 mins and 300-600 mU at 2 hrs whilst the experimental group received 40-80 mU at 40 mins and 280-
560 mU. Given there is inconsistency with the dose that the traditional group received, we can not include
study this as high-dose despite the upper limit of the dosing satisfying our definition of high-dose

Odem 1988 This study compared pulsed versus continuous infusions of oxytocin. The pulse group received a total oxytocin
of 7 mU at 40 mins and 93 mU at 2 hrs whilst the continuous group 50 mU at 40 mins and 450 mU at hrs.
Therefore, both groups would be classified into low-dose by this protocol

Oral 2003 The authors investigated the effect using oxytocin mixed with either isotonic 0.9% saline or 5% glucose
solution in women who required induction of labour. The oxytocin dose delivered was the same in both
groups

Orhue 1993b Both arms of the study describe an oxytocin infusion regimen that is high-dose according to our pre-specified
definition (Regimen 1: 100 mU by 40 mins, 900 mU by 120 mins, Regimen 2: 170 mU by 40 mins, 2370
mU by 120 mins)

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 33
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
(Continued)

Orhue 1994 Both arms of the study describe an oxytocin infusion regimen that is high-dose according to our pre-specified
definition (Regimen 1: 100 mU by 40 mins, 900 mU by 120 mins, Regimen 2: 170 mU by 40 mins, 2370
mU by 120 mins)

Parashi 2005 This study compared different oxytocin doses given at different intervals between 2 groups. Group A received
starting doses of 2.5 mU/min with increments of 2.5 mU/min every 15 mins (187.5 mU at 40 min and 1450
mU at 2 hrs) whilst group B received 5 mU/min and increased 5 mU/min every 45 mins (200 mU at 40 mins
and 1125 mU at 2 hrs). Therefore both groups would be classified into high-dose by this protocol

Parpas 1995 Oxytocin regimens vary according to weight so overall high-dose versus low-dose group comparisons are not
possible

Pavlou 1978 This study compared continuous versus pulsed delivery of oxytocin. The oxytocin dose that was delivered was
the same between both groups and only differed by delivery system

Reid 1995 This study compared pulsed oxytocin (28 mU at 40 min, 228 mU at 2 hrs) versus continuous infusion (50
mU at 40 min, 450 mU at 2 hrs). Both groups are classified as low-dose delivery by our protocol

Ross 1998 This study compared different starting and incremental doses with the timing of doses kept the same. In the
low-dose group women received 120 mU at 40 mins and 840 mU at 2 hrs whilst the high-dose group 360 mU
at 40 mins and 1980 mU at 2 hrs. Therefore both groups would be classified into high-dose by this protocol

Satin 1994 This trial was not randomised. It compared data of women undergoing induction where in the first 3 months
the hospital used a protocol of oxytocin increasing every 20 mins (360 mU at 40 mins and 2520 mU at 2 hrs)
and then the next 3 months used a protocol of oxytocin increasing every 40 mins (240 mU at 40 mins and
1440 mU at 2 hrs). Taking aside the methodological issues of this study, both groups would be classified into
high-dose by this protocol and therefore it is excluded

Steer 1985 All arms of the study (3 arms using standard labour ward infusion protocols and 1 arm using automatic
infusion system protocol) describe an oxytocin infusion regimen that is high-dose according to our prespecified
definition

Ustunyurt 2007 This study compared the continuation versus cessation of oxytocin at a cervical dilatation of 5 cm in women
requiring induction of labour. Both groups use the same dose schedule until 5 cm, then oxytocin was ceased
for 1 group, whilst continued for the other. The protocol used by the authors would be in the high-dose
category (150 mU at 40 mins, 950 mU at 2 hrs)

hr(s): hour
min(s): minutes
mU: milli units

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 34
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Characteristics of studies awaiting assessment [ordered by study ID]

Ashworth 1988

Methods Randomised controlled trial with allocation by sealed, numbered envelopes

Participants Women with singleton pregnancies greater than 37 weeks’ gestation requiring induction of labour with 3 or less
previous deliveries

Interventions Oxytocin by routine continuous infusion or pulsatile.

Outcomes Primary: duration of labour and total oxytocin dose. Secondary: volume of intravenous fluids, serum sodium changes,
jaundice of the newborn

Notes This remains unpublished to our knowledge and despite the record of study being retrieved, the only details found
were that it compared pulsed vs continuous infusion but not the dose of each group. No response from author for
further clarification

Raymond 1989

Methods Randomised controlled trial.

Participants 32 women at 39-42 weeks’ gestation.

Interventions Pulsed infusion of oxytocin vs continuous infusion.

Outcomes Mode of delivery, postpartum haemorrhage, fetal distress, total oxytocin dose, induction to delivery interval

Notes The authors assessed 32 women for induction of labour by using either pulsed or continuous oxytocin infusion.
The authors described the use of oxytocin in the pulsed group (40 mU at 40 mins, 120 mU at 2 hrs) but not the
continuous infusion group. No further contact from authors has been received

Salamalekis 2000

Methods Randomised controlled trial.

Participants 560 women greater than 37 weeks’ gestation undergoing induction of labour

Interventions Continuous oxytocin infusion vs pulsed oxytocin infusion.

Outcomes Induction to delivery interval, average dose of oxytocin, mode of delivery, Apgar score

Notes This randomised trial of 560 women compared continuous vs pulsatile oxytocin. The authors have reported the
continuous group received total oxytocin dose of 100 mU at 40 mins and 600 mU at 2 hrs whilst the pulsatile
group received a total oxytocin dose of 170 mU at 40 mins and 2850 mU at 2 hrs. This would classify both groups
into high-dose by this protocol, however the study appears to have misreported the pulsatile dose. The authors have
reported the dose as 2 mU/min and doubled every 15 mins but we have questioned if this is actually 2 mU/pulse.
Contact was attempted, however the authors have not replied

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 35
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Singh 1993

Methods Randomised trial using sealed opaque envelopes.

Participants 67 women admitted for induction of labour.

Interventions 5 units of syntocinon per litre in an infusion increased every 60 mins compared to 10 units of syntocinon per litre
in an infusion increased every 15 mins. No rate was supplied

Outcomes Non-statistically significant decrease induction to delivery time in the high-dose group. Higher rates of fetal heart
rate changes requiring syntocinon to be ceased in the high-dose group

Notes Dose information could not be obtained from abstract. No gestational age was supplied. Attempted to contact authors
without success

Sotunsa 2013

Methods Authors state randomised but no information about method.

Participants 136 women for induction of labour. No information provided on gestations or cause

Interventions Oxytocin. No explanation of initial or incremental dose. Groups were divided by interval timing of 30 vs 60 minutes

Outcomes Induction to delivery interval, fetal distress, meconium liquor, and NICU admission

Notes Unable to contact author. No publication despite poster presentation > 12 months prior to this review

hr: hour
min: minute
mU: milli units
NICU: neonatal intensive care unit
vs: versus

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 36
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
DATA AND ANALYSES

Comparison 1. High- versus low-dose oxytocin

No. of No. of
Outcome or subgroup title studies participants Statistical method Effect size

1 Vaginal delivery not achieved 2 1339 Risk Ratio (M-H, Fixed, 95% CI) 0.94 [0.78, 1.14]
within 24 hours
2 Caesarean section 8 2023 Risk Ratio (M-H, Fixed, 95% CI) 0.96 [0.81, 1.14]
3 Serious neonatal morbidity or 1 781 Risk Ratio (M-H, Fixed, 95% CI) 0.84 [0.23, 3.12]
perinatal death
4 Serious maternal morbidity or 1 523 Risk Ratio (M-H, Fixed, 95% CI) 1.24 [0.55, 2.82]
death
5 Time from induction to delivery 5 1725 Mean Difference (IV, Random, 95% CI) -0.90 [-2.28, 0.49]
6 Uterine hyperstimulation, fetal 5 876 Risk Ratio (M-H, Fixed, 95% CI) 1.86 [1.55, 2.25]
heart rate changes not specified
7 Uterine rupture 3 1429 Risk Ratio (M-H, Fixed, 95% CI) 3.10 [0.50, 19.33]
8 Epidural analgesia 2 1327 Risk Ratio (M-H, Random, 95% CI) 1.03 [0.89, 1.19]
9 Instrumental birth 3 693 Risk Ratio (M-H, Fixed, 95% CI) 1.22 [0.89, 1.66]
10 Apgar score less than seven at 5 1641 Risk Ratio (M-H, Fixed, 95% CI) 1.25 [0.77, 2.01]
five minutes
11 Perinatal death 2 1302 Risk Ratio (M-H, Fixed, 95% CI) 0.84 [0.23, 3.12]
12 Postpartum haemorrhage 5 1600 Risk Ratio (M-H, Fixed, 95% CI) 1.08 [0.87, 1.34]
13 Endometritis 3 1425 Risk Ratio (M-H, Random, 95% CI) 1.35 [0.53, 3.43]

Comparison 2. High- versus low-dose oxytocin: previous caesarean section or not

No. of No. of
Outcome or subgroup title studies participants Statistical method Effect size

1 Caesarean section 1 720 Risk Ratio (M-H, Fixed, 95% CI) 0.75 [0.50, 1.14]
1.1 Without previous 1 720 Risk Ratio (M-H, Fixed, 95% CI) 0.75 [0.50, 1.14]
caesarean section
1.2 With previous caesarean 0 0 Risk Ratio (M-H, Fixed, 95% CI) 0.0 [0.0, 0.0]
section

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Comparison 3. High- versus low-dose oxytocin: nulliparity or parity

No. of No. of
Outcome or subgroup title studies participants Statistical method Effect size

1 Uterine hyperstimulation, fetal 3 225 Risk Ratio (M-H, Random, 95% CI) 2.14 [1.40, 3.26]
heart rate changes not specified
1.1 Nulliparous subgroup 2 68 Risk Ratio (M-H, Random, 95% CI) 2.03 [1.15, 3.59]
1.2 Multiparous subgroup 3 157 Risk Ratio (M-H, Random, 95% CI) 2.50 [1.07, 5.84]
2 Caesarean section 5 849 Risk Ratio (M-H, Fixed, 95% CI) 0.89 [0.63, 1.25]
2.1 Nulliparous subgroup 4 591 Risk Ratio (M-H, Fixed, 95% CI) 0.75 [0.51, 1.10]
2.2 Multiparous subgroup 4 258 Risk Ratio (M-H, Fixed, 95% CI) 1.69 [0.77, 3.71]

Comparison 4. High- versus low-dose oxytocin: cervix unfavourable, favourable, or undefined

No. of No. of
Outcome or subgroup title studies participants Statistical method Effect size

1 Caesarean section 1 201 Risk Ratio (M-H, Fixed, 95% CI) 1.42 [0.68, 2.95]
1.1 Unfavourable cervix prior 1 105 Risk Ratio (M-H, Fixed, 95% CI) 1.56 [0.56, 4.31]
to induction
1.2 Favourable cervix prior to 1 96 Risk Ratio (M-H, Fixed, 95% CI) 1.29 [0.45, 3.70]
induction

Comparison 5. High- versus low-dose oxytocin: excluding studies at high risk of bias

No. of No. of
Outcome or subgroup title studies participants Statistical method Effect size

1 Caesarean section 2 611 Risk Ratio (M-H, Fixed, 95% CI) 1.01 [0.81, 1.25]
2 Induction to delivery interval 1 489 Mean Difference (IV, Fixed, 95% CI) -1.94 [-2.89, -0.99]
3 Uterine hyperstimulation, fetal 2 611 Risk Ratio (M-H, Fixed, 95% CI) 1.92 [1.51, 2.46]
heart rate changes not specified

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 38
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 1.1. Comparison 1 High- versus low-dose oxytocin, Outcome 1 Vaginal delivery not achieved
within 24 hours.
Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 1 Vaginal delivery not achieved within 24 hours

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI
Merrill 1999 24/404 25/412 17.8 % 0.98 [ 0.57, 1.69 ]

Tribe 2012 105/257 116/266 82.2 % 0.94 [ 0.77, 1.15 ]

Total (95% CI) 661 678 100.0 % 0.94 [ 0.78, 1.14 ]

Total events: 129 (High-dose), 141 (Low-dose)
Heterogeneity: Chi2 = 0.02, df = 1 (P = 0.88); I2 =0.0%
Test for overall effect: Z = 0.59 (P = 0.56)
Test for subgroup differences: Not applicable

0.5 0.7 1 1.5 2

Favours high-dose Favours low-dose

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 39
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 Analysis 1.2. Comparison 1 High- versus low-dose oxytocin, Outcome 2 Caesarean section.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 2 Caesarean section

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI

Crane 1993 13/61 10/69 4.7 % 1.47 [ 0.70, 3.11 ]

Dunn 1998 5/64 13/64 6.5 % 0.38 [ 0.15, 1.02 ]

Lowensohn 1990 7/25 8/30 3.6 % 1.05 [ 0.44, 2.49 ]

Merrill 1999 43/404 58/412 28.7 % 0.76 [ 0.52, 1.09 ]

Orhue 1993 4/44 2/46 1.0 % 2.09 [ 0.40, 10.85 ]

Satin 1991 5/48 1/32 0.6 % 3.33 [ 0.41, 27.22 ]

Tribe 2012 97/257 101/266 49.7 % 0.99 [ 0.80, 1.24 ]

Willcourt 1994 13/87 12/114 5.2 % 1.42 [ 0.68, 2.96 ]

Total (95% CI) 990 1033 100.0 % 0.96 [ 0.81, 1.14 ]

Total events: 187 (High-dose), 205 (Low-dose)
Heterogeneity: Chi2 = 9.70, df = 7 (P = 0.21); I2 =28%
Test for overall effect: Z = 0.50 (P = 0.62)
Test for subgroup differences: Not applicable

0.1 0.2 0.5 1 2 5 10

Favours high-dose Favours low-dose

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 40
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 Analysis 1.3. Comparison 1 High- versus low-dose oxytocin, Outcome 3 Serious neonatal morbidity or
perinatal death.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 3 Serious neonatal morbidity or perinatal death

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI
Merrill 1999 4/380 5/401 100.0 % 0.84 [ 0.23, 3.12 ]

Total (95% CI) 380 401 100.0 % 0.84 [ 0.23, 3.12 ]

Total events: 4 (High-dose), 5 (Low-dose)
Heterogeneity: not applicable
Test for overall effect: Z = 0.25 (P = 0.80)
Test for subgroup differences: Not applicable

0.01 0.1 1 10 100

Favours high-dose Favours low-dose

Analysis 1.4. Comparison 1 High- versus low-dose oxytocin, Outcome 4 Serious maternal morbidity or
death.
Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 4 Serious maternal morbidity or death

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI
Tribe 2012 12/257 10/266 100.0 % 1.24 [ 0.55, 2.82 ]

Total (95% CI) 257 266 100.0 % 1.24 [ 0.55, 2.82 ]

Total events: 12 (High-dose), 10 (Low-dose)
Heterogeneity: not applicable
Test for overall effect: Z = 0.52 (P = 0.61)
Test for subgroup differences: Not applicable

0.05 0.2 1 5 20
Favours high-dose Favours low-dose

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Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 1.5. Comparison 1 High- versus low-dose oxytocin, Outcome 5 Time from induction to delivery.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 5 Time from induction to delivery

Mean Mean
Study or subgroup High-dose Low-dose Difference Weight Difference
N Mean(SD)[hours] N Mean(SD)[hours] IV,Random,95% CI IV,Random,95% CI

Crane 1993 61 5.65 (2.83) 69 7.23 (2.73) 19.9 % -1.58 [ -2.54, -0.62 ]

Hourvitz 1996 80 8.92 (4.53) 59 8.67 (4.67) 17.2 % 0.25 [ -1.30, 1.80 ]

Merrill 1999 379 8.5 (0.3) 387 10.5 (0.3) 22.0 % -2.00 [ -2.04, -1.96 ]

Tribe 2012 246 9.33 (5.13) 243 11.27 (5.53) 19.9 % -1.94 [ -2.89, -0.99 ]

Willcourt 1994 87 7.25 (2.52) 114 6.29 (1.85) 21.0 % 0.96 [ 0.33, 1.59 ]

Total (95% CI) 853 872 100.0 % -0.90 [ -2.28, 0.49 ]

Heterogeneity: Tau2 = 2.27; Chi2 = 93.34, df = 4 (P<0.00001); I2 =96%
Test for overall effect: Z = 1.27 (P = 0.21)
Test for subgroup differences: Not applicable

-4 -2 0 2 4
Favours high-dose Favours low-dose

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 42
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 1.6. Comparison 1 High- versus low-dose oxytocin, Outcome 6 Uterine hyperstimulation, fetal
heart rate changes not specified.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 6 Uterine hyperstimulation, fetal heart rate changes not specified

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI

Crane 1993 32/61 23/69 19.6 % 1.57 [ 1.04, 2.37 ]

Lowensohn 1990 18/25 8/30 6.6 % 2.70 [ 1.42, 5.13 ]

Orhue 1993 17/44 4/46 3.6 % 4.44 [ 1.62, 12.17 ]

Satin 1991 26/48 11/32 12.0 % 1.58 [ 0.91, 2.72 ]

Tribe 2012 112/257 65/264 58.2 % 1.77 [ 1.37, 2.28 ]

Total (95% CI) 435 441 100.0 % 1.86 [ 1.55, 2.25 ]

Total events: 205 (High-dose), 111 (Low-dose)
Heterogeneity: Chi2 = 5.32, df = 4 (P = 0.26); I2 =25%
Test for overall effect: Z = 6.50 (P < 0.00001)
Test for subgroup differences: Not applicable

0.05 0.2 1 5 20
Favours high-dose Favours low-dose

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 43
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 1.7. Comparison 1 High- versus low-dose oxytocin, Outcome 7 Uterine rupture.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 7 Uterine rupture

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI
Merrill 1999 1/404 1/412 66.9 % 1.02 [ 0.06, 16.25 ]

Orhue 1993 3/44 0/46 33.1 % 7.31 [ 0.39, 137.59 ]

Tribe 2012 0/257 0/266 Not estimable

Total (95% CI) 705 724 100.0 % 3.10 [ 0.50, 19.33 ]

Total events: 4 (High-dose), 1 (Low-dose)
Heterogeneity: Chi2 = 0.95, df = 1 (P = 0.33); I2 =0.0%
Test for overall effect: Z = 1.21 (P = 0.23)
Test for subgroup differences: Not applicable

0.01 0.1 1 10 100

Favours high-dose Favours low-dose

Analysis 1.8. Comparison 1 High- versus low-dose oxytocin, Outcome 8 Epidural analgesia.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 8 Epidural analgesia

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

M- M-
H,Random,95% H,Random,95%
n/N n/N CI CI
Merrill 1999 273/404 291/412 52.6 % 0.96 [ 0.87, 1.05 ]

Tribe 2012 187/253 172/258 47.4 % 1.11 [ 0.99, 1.24 ]

Total (95% CI) 657 670 100.0 % 1.03 [ 0.89, 1.19 ]

Total events: 460 (High-dose), 463 (Low-dose)
Heterogeneity: Tau2 = 0.01; Chi2 = 3.93, df = 1 (P = 0.05); I2 =75%
Test for overall effect: Z = 0.35 (P = 0.73)
Test for subgroup differences: Not applicable

0.5 0.7 1 1.5 2

Favours high-dose Favours low-dose

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Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 1.9. Comparison 1 High- versus low-dose oxytocin, Outcome 9 Instrumental birth.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 9 Instrumental birth

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI
Orhue 1993 5/44 4/46 6.8 % 1.31 [ 0.38, 4.55 ]

Satin 1991 2/48 2/32 4.2 % 0.67 [ 0.10, 4.49 ]

Tribe 2012 62/257 52/266 89.0 % 1.23 [ 0.89, 1.71 ]

Total (95% CI) 349 344 100.0 % 1.22 [ 0.89, 1.66 ]

Total events: 69 (High-dose), 58 (Low-dose)
Heterogeneity: Chi2 = 0.40, df = 2 (P = 0.82); I2 =0.0%
Test for overall effect: Z = 1.23 (P = 0.22)
Test for subgroup differences: Not applicable

0.01 0.1 1 10 100

Favours high-dose Favours low-dose

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Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 1.10. Comparison 1 High- versus low-dose oxytocin, Outcome 10 Apgar score less than seven at
five minutes.
Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 10 Apgar score less than seven at five minutes

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI
Dunn 1998 3/64 1/64 3.5 % 3.00 [ 0.32, 28.08 ]

Hourvitz 1996 4/83 3/65 11.6 % 1.04 [ 0.24, 4.50 ]

Merrill 1999 22/380 22/401 74.0 % 1.06 [ 0.59, 1.87 ]

Satin 1991 1/48 1/32 4.1 % 0.67 [ 0.04, 10.28 ]

Tribe 2012 6/247 2/257 6.8 % 3.12 [ 0.64, 15.32 ]

Total (95% CI) 822 819 100.0 % 1.25 [ 0.77, 2.01 ]

Total events: 36 (High-dose), 29 (Low-dose)
Heterogeneity: Chi2 = 2.45, df = 4 (P = 0.65); I2 =0.0%
Test for overall effect: Z = 0.90 (P = 0.37)
Test for subgroup differences: Not applicable

0.01 0.1 1 10 100

Favours high-dose Favours low-dose

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 46
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 1.11. Comparison 1 High- versus low-dose oxytocin, Outcome 11 Perinatal death.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 11 Perinatal death

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI
Merrill 1999 4/380 5/401 100.0 % 0.84 [ 0.23, 3.12 ]

Tribe 2012 0/257 0/264 Not estimable

Total (95% CI) 637 665 100.0 % 0.84 [ 0.23, 3.12 ]

Total events: 4 (High-dose), 5 (Low-dose)
Heterogeneity: not applicable
Test for overall effect: Z = 0.25 (P = 0.80)
Test for subgroup differences: Not applicable

0.01 0.1 1 10 100

Favours high-dose Favours low-dose

Analysis 1.12. Comparison 1 High- versus low-dose oxytocin, Outcome 12 Postpartum haemorrhage.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 12 Postpartum haemorrhage

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI

Hourvitz 1996 4/83 2/65 2.0 % 1.57 [ 0.30, 8.29 ]

Merrill 1999 15/379 19/387 16.6 % 0.81 [ 0.42, 1.56 ]

Orhue 1993 10/44 4/46 3.5 % 2.61 [ 0.88, 7.72 ]

Satin 1991 0/48 0/32 Not estimable

Tribe 2012 95/262 87/254 78.0 % 1.06 [ 0.84, 1.34 ]

Total (95% CI) 816 784 100.0 % 1.08 [ 0.87, 1.34 ]

Total events: 124 (High-dose), 112 (Low-dose)
Heterogeneity: Chi2 = 3.53, df = 3 (P = 0.32); I2 =15%
Test for overall effect: Z = 0.70 (P = 0.48)
Test for subgroup differences: Not applicable

0.1 0.2 0.5 1 2 5 10

Favours high-dose Favours low-dose

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Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 1.13. Comparison 1 High- versus low-dose oxytocin, Outcome 13 Endometritis.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 1 High- versus low-dose oxytocin

Outcome: 13 Endometritis

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

M- M-
H,Random,95% H,Random,95%
n/N n/N CI CI
Hourvitz 1996 4/83 2/65 23.4 % 1.57 [ 0.30, 8.29 ]

Merrill 1999 6/379 9/387 43.5 % 0.68 [ 0.24, 1.89 ]

Tribe 2012 9/257 3/254 33.1 % 2.96 [ 0.81, 10.83 ]

Total (95% CI) 719 706 100.0 % 1.35 [ 0.53, 3.43 ]

Total events: 19 (High-dose), 14 (Low-dose)
Heterogeneity: Tau2 = 0.25; Chi2 = 3.14, df = 2 (P = 0.21); I2 =36%
Test for overall effect: Z = 0.62 (P = 0.53)
Test for subgroup differences: Not applicable

0.01 0.1 1 10 100

Favours high-dose Favours low-dose

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Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 2.1. Comparison 2 High- versus low-dose oxytocin: previous caesarean section or not, Outcome 1
Caesarean section.
Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 2 High- versus low-dose oxytocin: previous caesarean section or not

Outcome: 1 Caesarean section

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI

1 Without previous caesarean section

Merrill 1999 35/358 47/362 100.0 % 0.75 [ 0.50, 1.14 ]

Subtotal (95% CI) 358 362 100.0 % 0.75 [ 0.50, 1.14 ]

Total events: 35 (High-dose), 47 (Low-dose)
Heterogeneity: not applicable
Test for overall effect: Z = 1.35 (P = 0.18)
2 With previous caesarean section
Subtotal (95% CI) 0 0 Not estimable
Total events: 0 (High-dose), 0 (Low-dose)
Heterogeneity: not applicable
Test for overall effect: not applicable
Total (95% CI) 358 362 100.0 % 0.75 [ 0.50, 1.14 ]
Total events: 35 (High-dose), 47 (Low-dose)
Heterogeneity: not applicable
Test for overall effect: Z = 1.35 (P = 0.18)
Test for subgroup differences: Not applicable

0.5 0.7 1 1.5 2

Favours high-dose Favours low-dose

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 Analysis 3.1. Comparison 3 High- versus low-dose oxytocin: nulliparity or parity, Outcome 1 Uterine
hyperstimulation, fetal heart rate changes not specified.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 3 High- versus low-dose oxytocin: nulliparity or parity

Outcome: 1 Uterine hyperstimulation, fetal heart rate changes not specified

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

M- M-
H,Random,95% H,Random,95%
n/N n/N CI CI

1 Nulliparous subgroup
Lowensohn 1990 10/14 6/17 25.9 % 2.02 [ 0.98, 4.17 ]

Satin 1991 12/22 4/15 17.6 % 2.05 [ 0.81, 5.14 ]

Subtotal (95% CI) 36 32 43.5 % 2.03 [ 1.15, 3.59 ]

Total events: 22 (High-dose), 10 (Low-dose)
Heterogeneity: Tau2 = 0.0; Chi2 = 0.00, df = 1 (P = 0.99); I2 =0.0%
Test for overall effect: Z = 2.44 (P = 0.015)
2 Multiparous subgroup
Lowensohn 1990 8/11 2/13 9.3 % 4.73 [ 1.26, 17.79 ]

Orhue 1993 17/44 5/46 18.1 % 3.55 [ 1.43, 8.81 ]

Satin 1991 14/26 7/17 29.1 % 1.31 [ 0.67, 2.56 ]

Subtotal (95% CI) 81 76 56.5 % 2.50 [ 1.07, 5.84 ]

Total events: 39 (High-dose), 14 (Low-dose)
Heterogeneity: Tau2 = 0.33; Chi2 = 4.95, df = 2 (P = 0.08); I2 =60%
Test for overall effect: Z = 2.12 (P = 0.034)
Total (95% CI) 117 108 100.0 % 2.14 [ 1.40, 3.26 ]
Total events: 61 (High-dose), 24 (Low-dose)
Heterogeneity: Tau2 = 0.04; Chi2 = 4.88, df = 4 (P = 0.30); I2 =18%
Test for overall effect: Z = 3.53 (P = 0.00041)
Test for subgroup differences: Chi2 = 0.16, df = 1 (P = 0.69), I2 =0.0%

0.5 0.7 1 1.5 2

Favours high-dose Favours low-dose

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 Analysis 3.2. Comparison 3 High- versus low-dose oxytocin: nulliparity or parity, Outcome 2 Caesarean
section.
Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 3 High- versus low-dose oxytocin: nulliparity or parity

Outcome: 2 Caesarean section

Study or subgroup High-dose Low-dose Risk Ratio Weight Risk Ratio

n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI

1 Nulliparous subgroup
Lowensohn 1990 5/14 6/17 9.1 % 1.01 [ 0.39, 2.62 ]

Merrill 1999 24/207 37/216 60.6 % 0.68 [ 0.42, 1.09 ]

Satin 1991 3/22 1/15 2.0 % 2.05 [ 0.23, 17.84 ]

Willcourt 1994 7/58 7/42 13.6 % 0.72 [ 0.27, 1.91 ]

Subtotal (95% CI) 301 290 85.2 % 0.75 [ 0.51, 1.10 ]

Total events: 39 (High-dose), 51 (Low-dose)
Heterogeneity: Chi2 = 1.39, df = 3 (P = 0.71); I2 =0.0%
Test for overall effect: Z = 1.46 (P = 0.15)
2 Multiparous subgroup
Lowensohn 1990 2/11 2/13 3.1 % 1.18 [ 0.20, 7.06 ]

Orhue 1993 4/44 2/46 3.3 % 2.09 [ 0.40, 10.85 ]

Satin 1991 2/26 0/17 1.0 % 3.33 [ 0.17, 65.44 ]

Willcourt 1994 6/45 5/56 7.5 % 1.49 [ 0.49, 4.58 ]

Subtotal (95% CI) 126 132 14.8 % 1.69 [ 0.77, 3.71 ]

Total events: 14 (High-dose), 9 (Low-dose)
Heterogeneity: Chi2 = 0.46, df = 3 (P = 0.93); I2 =0.0%
Test for overall effect: Z = 1.30 (P = 0.19)
Total (95% CI) 427 422 100.0 % 0.89 [ 0.63, 1.25 ]
Total events: 53 (High-dose), 60 (Low-dose)
Heterogeneity: Chi2 = 4.78, df = 7 (P = 0.69); I2 =0.0%
Test for overall effect: Z = 0.67 (P = 0.50)
Test for subgroup differences: Chi2 = 3.25, df = 1 (P = 0.07), I2 =69%

0.5 0.7 1 1.5 2

Favours high-dose Favours low-dose

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 Analysis 4.1. Comparison 4 High- versus low-dose oxytocin: cervix unfavourable, favourable, or undefined,
Outcome 1 Caesarean section.
Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 4 High- versus low-dose oxytocin: cervix unfavourable, favourable, or undefined

Outcome: 1 Caesarean section

Study or subgroup Favours high-dose Favours low-dose Risk Ratio Weight Risk Ratio
n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI

1 Unfavourable cervix prior to induction

Willcourt 1994 7/45 6/60 49.5 % 1.56 [ 0.56, 4.31 ]

Subtotal (95% CI) 45 60 49.5 % 1.56 [ 0.56, 4.31 ]

Total events: 7 (Favours high-dose), 6 (Favours low-dose)
Heterogeneity: not applicable
Test for overall effect: Z = 0.85 (P = 0.40)
2 Favourable cervix prior to induction
Willcourt 1994 6/42 6/54 50.5 % 1.29 [ 0.45, 3.70 ]

Subtotal (95% CI) 42 54 50.5 % 1.29 [ 0.45, 3.70 ]

Total events: 6 (Favours high-dose), 6 (Favours low-dose)
Heterogeneity: not applicable
Test for overall effect: Z = 0.47 (P = 0.64)
Total (95% CI) 87 114 100.0 % 1.42 [ 0.68, 2.95 ]
Total events: 13 (Favours high-dose), 12 (Favours low-dose)
Heterogeneity: Chi2 = 0.06, df = 1 (P = 0.80); I2 =0.0%
Test for overall effect: Z = 0.94 (P = 0.35)
Test for subgroup differences: Chi2 = 0.06, df = 1 (P = 0.80), I2 =0.0%

0.2 0.5 1 2 5
Favours high-dose Favours low-dose

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 Analysis 5.1. Comparison 5 High- versus low-dose oxytocin: excluding studies at high risk of bias, Outcome
1 Caesarean section.
Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 5 High- versus low-dose oxytocin: excluding studies at high risk of bias

Outcome: 1 Caesarean section

Study or subgroup High dose Low dose Risk Ratio Weight Risk Ratio
n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI
Tribe 2012 97/257 101/264 98.1 % 0.99 [ 0.79, 1.23 ]

Orhue 1993 4/44 2/46 1.9 % 2.09 [ 0.40, 10.85 ]

Total (95% CI) 301 310 100.0 % 1.01 [ 0.81, 1.25 ]

Total events: 101 (High dose), 103 (Low dose)
Heterogeneity: Chi2 = 0.79, df = 1 (P = 0.37); I2 =0.0%
Test for overall effect: Z = 0.07 (P = 0.94)
Test for subgroup differences: Not applicable

0.01 0.1 1 10 100

Favours low-dose Favours high-dose

Analysis 5.2. Comparison 5 High- versus low-dose oxytocin: excluding studies at high risk of bias, Outcome
2 Induction to delivery interval.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 5 High- versus low-dose oxytocin: excluding studies at high risk of bias

Outcome: 2 Induction to delivery interval

Mean Mean
Study or subgroup High dose Low dose Difference Weight Difference
N Mean(SD) N Mean(SD) IV,Fixed,95% CI IV,Fixed,95% CI

Tribe 2012 246 9.33 (5.13) 243 11.27 (5.53) 100.0 % -1.94 [ -2.89, -0.99 ]

Total (95% CI) 246 243 100.0 % -1.94 [ -2.89, -0.99 ]

Heterogeneity: not applicable
Test for overall effect: Z = 4.02 (P = 0.000058)
Test for subgroup differences: Not applicable

-100 -50 0 50 100

Favours High dose Favours low dose

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 53
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
 Analysis 5.3. Comparison 5 High- versus low-dose oxytocin: excluding studies at high risk of bias, Outcome
3 Uterine hyperstimulation, fetal heart rate changes not specified.

Review: High-dose versus low-dose oxytocin infusion regimens for induction of labour at term

Comparison: 5 High- versus low-dose oxytocin: excluding studies at high risk of bias

Outcome: 3 Uterine hyperstimulation, fetal heart rate changes not specified

Study or subgroup High dose Low dose Risk Ratio Weight Risk Ratio
n/N n/N M-H,Fixed,95% CI M-H,Fixed,95% CI
Orhue 1993 17/44 4/46 5.7 % 4.44 [ 1.62, 12.17 ]

Tribe 2012 112/257 65/264 94.3 % 1.77 [ 1.37, 2.28 ]

Total (95% CI) 301 310 100.0 % 1.92 [ 1.51, 2.46 ]

Total events: 129 (High dose), 69 (Low dose)
Heterogeneity: Chi2 = 3.07, df = 1 (P = 0.08); I2 =67%
Test for overall effect: Z = 5.24 (P < 0.00001)
Test for subgroup differences: Not applicable

0.01 0.1 1 10 100

Favours High-dose Favours Low-dose

WHAT’S NEW
Last assessed as up-to-date: 31 August 2014.

Date Event Description

21 March 2016 Amended We have clarified the subgroups in Analysis 2.1 caesarean section - existing data relate to women
without a previous caesarean section. There are no data pertaining to a subgroup of women who had
a previous caesarean section

CONTRIBUTIONS OF AUTHORS
A Budden and A Henry wrote the protocol.
L Chen reviewed all retrieved studies, with either A Budden or A Henry providing second assessment on each paper for its inclusion
or exclusion.
A Budden, A Henry, and L Chen each reviewed the included papers and co-authored the review.
Emily Bain provided author support for the review.

High-dose versus low-dose oxytocin infusion regimens for induction of labour at term (Review) 54
Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
DECLARATIONS OF INTEREST
None known.

SOURCES OF SUPPORT

Internal sources
• Australian Research Centre for Health of Women and Babies (ARCH), Australia.

External sources
• Department of Health and Ageing, Australian Government, Australia.

DIFFERENCES BETWEEN PROTOCOL AND REVIEW

The title of this review has changed since publication of the protocol (Budden 2012). The protocol was entitled, ’Oxytocin infusion
regimens for induction of labour’ but during the preparation of the full review this title was changed to ’High-dose versus low-dose oxytocin
infusion regimens for induction of labour at term’.
A post-hoc secondary outcome, uterine hyperstimulation (fetal heart rate changes unknown), was added as a majority of studies reported
uterine hyperstimulation but not its effect on fetal heart rate and therefore could not be placed into the protocols pre-specified outcomes.
No studies had specified uterine hyperstimulation without fetal heart rate changes and as such it was not reported on in favour of this
post-hoc outcome.
Inclusion criteria - despite inclusion criteria of gestation from 24 weeks, the study by Merrill 1999 was included as the average gestation
was 38 weeks such with a narrow confidence interval that minimal if any women would have been preterm. Given the size of the review
it was felt to keep this trial and adjust results in sensitivity where possible.
No other changes from the protocol were made.

INDEX TERMS

Medical Subject Headings (MeSH)

∗ Term Birth; Labor, Induced [∗ methods]; Oxytocics [∗ administration & dosage; adverse effects]; Oxytocin [∗ administration & dosage;

adverse effects]; Randomized Controlled Trials as Topic

MeSH check words

Female; Humans; Pregnancy

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Copyright © 2016 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.