Review

Uterine artery Doppler flow studies in obstetric

Rosalba Giordano1 of the maternal uterine vessels, and this could offers the
Alessandra Cacciatore1 potential to detect women at risk for diseases like pree-
Mattea Romano1 clampsia.
Beatrice La Rosa2 Also, abnormal uterine artery Doppler studies in both the
Ilenia Fonti2 first and second trimester have been shown to be asso-
ciated with subsequent perinatal complications.
Roberto Vigna3
1
Department of Obstetrics and Gynecology of “S.
Uterine artery Doppler studies in normal pregnancy
Bambino” Hospital. University of Catania, Italy.
2
Department of Obstetrics and Gynecology, Policlinico-
Schulman and colleagues determined that in the non
Vittorio Emanuele. University of Catania, Italy
pregnant state there is a rapid rise and fall in uterine ar-
3
Fetal-Maternal Medical Centre “Artemisia”, Depart-
ment of Prenatal Diagnosis, Rome, Italy tery flow velocity during systole and a “notch” in the de-
scending waveform in early diastole. During pregnancy,
Corresponding author: they noted a significant increase in uterine artery com-
Rosalba Giordano pliance between 8 and 16 weeks, which continued to a
Department of Obstetrics and Gynecology, Policlinico- lesser extent until 26 weeks’ gestation (2).
“Vittorio Emanuele”. University of Catania, Italy The majority of research has centered on an elevation in
e-mail: rosalbagiordano@virgilio.it the RI or PI, or the persistence of a uterine artery dias-
tolic notch to detect the presence of increased uteropla-
cental vascular resistance. Criteria for an abnormal RI
Summary have varied from a single cut off (eg, RI > 0.58) to a per-
centile cut off value (eg, 75 th, 90 th, 95 th). The Gomez
In women who develop preeclampsia there is a et al evaluated the uterine artery PI in the first trimester,
pathological increase in placental vascular resist- and was able to identify 30.8% of pregnancies that sub-
ance should be detectable by abnormal Doppler sequently developed severe pregnancy complications
flow studies of the maternal uterine vessels. by using the 95th percentile as a cut off (3).
In women considered at low risk with abnormal ear- In order to increase the sensitivity and specificity of this
ly pregnancy uterine artery Doppler studies are technique Papageorghiou et al9 combined maternal his-
needed. Until such time as these are available, rou- tory with uterine artery Doppler to determine a patient’s
tine uterine artery Doppler screening of women con- specific risk. Accepting a false positive rate of 25%, they
sidered at low risk is not recommended. Uterine ar- were able to identify 67.5% of women who would subse-
tery Doppler screening of high-risk women appears quently develop preeclampsia (4). A recent metanalysis
to identify those at substantially increased risk for concluded that a PI with notching had the best predictive
adverse pregnancy outcomes. and interventions value for pregnancy outcomes (5). It appears that as the
that might improve clinical outcomes. impedance to flow increases in the placenta there is in
Abnormal testing in these women could potentially late systole or early diastole, or an increase in down-
lead to increased surveillance and interventions stream resistance as the relatively inflexible distal artery
that might improve clinical outcomes. recoils from distention caused by the systolic pulse. This
is manifested as an early diastolic notch in the Doppler
Key words: uterine artery, Doppler flow, preeclampsia, SGA. wave form. Most studies use subjective criteria for the
definition of a diastolic notch, but a drop of at least a 50
cm/s from the maximum diastolic velocity is a reason-
Introduction able criterion after 20 weeks (6). In a screening program
of 2058 unselected women, Bower et al identified
In normal pregnancy, placental trophoblast cells invade women with a uterine artery diastolic notch present or a
the inner third of the myometrium and migrate the entire high RI (95 th percentiles) at 18-22 weeks, and repeat-
length of the maternal spiral arteries what optimizes de- ed testing for these women at 24 weeks (7). Uterine ar-
livery of oxygen and nutrients to the fetus. In women tery notching was defined subjectively but the authors
who develop preeclampsia there is failure of trophoblast demonstrated concordance in subjective criteria among
invasion of the uterine muscalar wall with the result that sonographers before the study was performed. Three
the spiral arteries retain the muscle elastic coating and hundred twenty-nine (16%) women had abnormal RI
impedance to blood flow persists (1). Theoretically, a values and/or uterine artery notching on the first evalua-
pathological increase in placental vascular resistance tion, with 104 women having persistently abnormal test-
should be detectable by abnormal Doppler flow studies ing. The presence of a diastolic notch was a better pre-

Journal of Prenatal Medicine 2010; 4 (4): 59-62 59

dictor of preeclampsia than an elevated RI. quent development of preeclampsia (95% confidence
In an evaluation of women at increased risk for interval (CI), 5.7-7.1), and a negative result carried an
preeclampsia or growth restriction, compared the diag- LR of 0.7 (95% CI, 0.6-0.8). Women with a positive test
nostic accuracy of gestational-aged adjusted 90th and had an LR of 3.6 (95% CI, 3.2-4.0) for the development
95th percentile cut offs for RI at 20, 28, 36 weeks’ gesta- of fetal growth restriction and a negative result carried a
tion with a cut off of 0.58, and the presence or absence 0.8 LR (95% CI, 0.8-0.9). Results for the prediction of
of a diastolic notch. They concluded that 20 weeks’ ges- perinatal death were less robust with an LR of 1.8 (95%
tation was the optimal time for testing, with an abnormal CI, 1.2-2.9) for a positive test result, and 0.9 (95% CI,
value being defined as above the 90th percentile. The 0.8-1.1) for a negative result. A recent metanalysis found
presence of a diastolic notch carried a 57% positive pre- a positive LR for preeclampsia of 7.5 (95% CI, 5.4-10.2)
dictive value for subsequent severe complications and and a negative LR of 0.59 (95% CI, 0.47-0.71), and for
93% predictive value for any complication (8). Although severe preeclampsia a positive LR of 15.6 (95% CI,
this combination had the strongest positive predictive 13.3- 17.3) and a negative LR of 0.4 (95% CI, 0.2-0.6).
value, the sensitivity remained low for any complications Furthermore, in women with abnormal uterine artery
(21%) and for severe complications (27%). In summary, Doppler studies a positive LR of 9.1 (95% CI, 5.0-16.7)
there are no current standards for gestational age at test- and a negative LR of 0.89 (95% CI, 0.85- 0.93) were
ing or criteria for an abnormal uterine artery Doppler found for the occurrence of growth restriction (13).
study. Once adequately trained in the technique, a rea-
sonable approach would be to use an ultrasound ma-
chine with the capability to perform continuous wave Abnormal uterine artery Doppler studies: treatment
and/or pulsed wave Doppler studies of the uterine, arcu- of women considered at low risk
ate, and subplacental arteries. In 1 report, a proper
waveform could be obtained within 20 minutes in all cas- Several studies have evaluated the potential benefits of
es (9). The RI, with gestational age appropriate cut offs, therapeutic interventions for those with abnormal uter-
is the most commonly used index. However, (8) Chan et ine artery Doppler studies. One of the largest, by
al. showed little difference between using a RI >0.58 or a Goffinet et al, was a multicenter trial of 3317 pregnant
RI above the 95 th percentile, and both were more effec- women (14). Low risk gravidas with an abnormal uter-
tive at predicting an adverse outcome when combined ine artery Doppler between 20 and 24 weeks’ gestation
with the presence of a diastolic notch (8,9). A reasonable were treated with of 150 mg aspirin daily until 36 weeks’
definition for a diastolic notch is a drop of at least 50 cm/s gestation. They found no significant reduction of in-
from the maximum diastolic velocity. PI has been less trauterine growth restriction and preeclampsia when
commonly reported, but using levels above the 95 th per- these women were compared with women who did not
centile or a PI>1.6 appears to be appropriate. Recent re- receive aspirin therapy, and concluded that there was
ports show some utility in assessment of uterine artery no justification for screening and treatment with uterine
flow in the first trimester. However, the second trimester artery Doppler in low risk populations. In a analysis of a
has yielded more consistent results. Performance at 18- recently published prospective study of antioxidant
20 weeks’gestation is a reasonable approach. There is therapy for the prevention of preeclampsia that found
some evidence that repeating the tests at 24-26 weeks no significant benefit from 1000 mg of vitamin C and
may add further benefit (10). 400 IU of vitamin E given daily to at-risk woman, those
with abnormal uterine Doppler studies at 18-22 weeks’
gestation also failed to benefit from therapy (preeclamp-
Screening in low risk populations sia; 24% vs 25%; relative risk (RR), 0.95; 95% CI, 0.40-
2.29;) (15).
Abnormal uterine artery Doppler studies in both the first
and second trimesters have been shown to be associat-
ed with subsequent perinatal complications. For women Screening in high risk populations
with abnormal testing in the first trimester, the likelihood
ratio (LR) for the development of preeclampsia is ap- Restriction of screening to populations at increased risk
proximately 5, while those with normal Doppler flow for adverse outcomes can improve the predictive value
studies have an LR of 0.5. Similarly, an abnormal test of the test. Based on this principle it is plausible that uter-
carries an LR of 2 for fetal growth restriction, with an LR ine artery Doppler studies could prove more useful when
of 0.9 after a normal test result. Though this relationship performed on at-risk women. The metanalysis by Chien
persists with testing in the second trimester, the sensitiv- et al included 12 studies of high risk patients which met
ity may be lower (11). However, Antsaklis et al found the stringent inclusion criteria (13). The LR for preeclampsia
sensitivity and specificity of screening for preeclampsia after an abnormal test was 2.8 (95% CI, 2.3-3.4), result-
to be 81% and 87% at 20 weeks, and 76% and 95% at ing in an increase in the pretest probability from 9.8-23%.
24 weeks’ gestation (12). Similar results were obtained for the prediction of fetal
The utility of uterine artery Doppler assessment was growth restriction, with an LR of 2.7 (95% CI, 2.1-3.4),
published by Chien and colleagues in 2000 (13). Strict with the probability increasing from 17.8-36.7% with a
criteria regarding diagnostic interventions and outcome positive test. The LR of perinatal death after an abnormal
measures were used for inclusion. Twenty-eight studies test was 4.0 (95% CI, 2.4-6.6), increasing the pretest
met their criteria, encompassing a total of 12,994 pa- probability from 8.9-27.8%. A recent metanalysis on uter-
tients. Analysis of studies involving low risk populations ine artery Doppler and adverse pregnancy outcomes in
revealed that an abnormal velocity waveform with or high risk gravidas included 83 studies with approximate-
without a diastolic notch carried an LR of 6.4 for subse- ly 18,000 women, and found that the presence of notch-

60 Journal of Prenatal Medicine 2010; 4 (4): 59-62

ing had a positive LR of 20.2 (95% CI, 7.5-29.5) and a are amenable to such screening, what testing regimen is
negative LR of 0.17 (95% CI, 0.03-0.56) for preeclamp- optimal for a normal or abnormal test in these women,
sia. In the same analysis women with an RI > 0.58 had a and what interventions based on these findings will im-
positive LR of 10.9 (95% CI, 10.4-11.4) and negative LR prove pregnancy outcomes. At this time, the evidence
of 0.20 (95% CI, 10.4-11.4) for growth restriction. Though does not support routine screening with uterine artery
an effective intervention to avoid complications has not Doppler in any particular group of patients.
been identified for high risk women with an abnormal
uterine artery Doppler study, it is plausible that testing
could be used to select those who are at lower risk based References
on a reassuring test.
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study is needed to determine which high-risk conditions ing with a uterine Doppler in low risk pregnant

Journal of Prenatal Medicine 2010; 4 (4): 59-62 61

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62 Journal of Prenatal Medicine 2010; 4 (4): 59-62