DYSTOCIA

I. DYSTOCIA
1. Means difficult labor or prolonged labor
2. Characterized by abnormally slow progress of labor
3. The most common indication for primary CS delivery
4. Contributing factor in >70% of maternal death
5. Could be due to any abnormalities of (Williams 25th Ed):
1. Power (uterine contractility and maternal expulsive
effort)
2. Passenger (fetus)
3. Passages (pelvis and lower reproductive tract)

A. CAUSES
6. True Labor Figure 1. Friedman Curve
1. Uterine contraction that bring about demonstrable
effacement and dilation of the cervix D. PHASES OF CERVICAL DILATATION
2. It does not need pain for it to become true labor 9. Preparatory division of labor
3. Note: normal spontaneous vaginal delivery requires 10. Commences with maternal perception of
not only dilatation, head descent must also occur. regular uterine contraction
7. When does labor start? Latent
Phase 11. Accompanied by progressive cervical
1. When painful contractions become regular dilatation and ends between 3-4 cm
2. At the time of admission to the labor unit dilatation
8. Duration of labor = time elapsed from admission to 12. 10% are false labor
delivery 13. Cervical dilatation of 3-5 cm or more, in
the presence of uterine contractions, can
B. STAGES OF LABOR reliably represent the threshold for active
1st From regular uterine contraction to full cervical labor
Stage dilatation (10cm) 1. Acceleration phase
Full cervical dilatation of the cervix up to the delivery  Determines the ultimate outcome of labor
2nd of the baby  Faster acceleration, faster dilatation, faster
Stage NULLIPARA - Average 50 minutes Active
delivery
- 2-3 hours if w/ regional anesthesia Phase
2. Phase of maximum slope
Hardes - 2 hours if w/o regional anesthesia
t part of MULTIPAR - Average 20 minutes  Good measure of overall efficiency of the
all the A - 1-2 hours if w/ regional anesthesia uterus/machine
stages *NULLIPARA – never completed pregnancy beyond  Uterus is contracting well
20 weeks gestation 3. Deceleration phase
3rd  Reflects feto-pelvic relationship
From the delivery of the baby to placental expulsion
Stage
 Starts at 7-8 cm dilatation
C. FUNCTIONAL DIVISION OF LABOR
1. PREPARATORY
1. Includes the latent and acceleration phase
2. Sensitive to sedation and analgesia
3. Change in the connective tissue components of the
cervix (cervical softening)
2. DILATATIONAL
1. Dilatation occurs at most rapid rate
2. Unaffected by sedation
1. Corresponds to rapid dilatation of cervix
3. PELVIC
1. Commences with deceleration phase
2. Cardinal movement of labor occur (EDFIREERE)
1. Engagement > Descent > Flexion > Internal
Rotation > Extension > External Rotation > Figure 2. Dilatational and descent patterns
Expulsion
3. In actual practice, however, the onset of pelvic 14. Cervical dilatation: sigmoidal curve
division is seldom clearly identifiable 15. Fetal head descent: hyperbolic curve
16. Average rate of descent of fetal head
1. Nullipara: 1cm/hr
1. (begins deceleration phase at about 7-8cm
dilated)
2. Multipara: 2cm/hr

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 E. WHO PARTOGRAPH (1994, Modified 2006)
17. No latent phase (after modification in 2006)
18. Should be started in women with active labor (4cm
cervical dilatation)
19. It has 2 sets of observation
1. 1st set - relate to progress of cervical dilatation,
descent of fetal head and uterine contractions
2. 2nd set - focuses on the fetus, fetal heart rate,
membranes, amniotic fluid and molding of head

20. Women in labor (parturient) should be

referred to a hospital when cervical
dilatation moves to the right of the
ALERT alert line
LINE 21. Management:
1. Artificial rupture of membrane
(AROM) Figure 4. Cervical dilatation (Friedman vs Zhang)
2. Close observation
22. If labor crosses the action line (4 Table 1. Comparison between Friedman and Zhang’s Labor Patterns
hours to the right of alert line) Classic Labor Contemporary Labor
Features
23. It requires active intervention Pattern (Friedman) Patterns (Zhang)
ACTION 24. Management: Threshold
LINE 1. Provide analgesia for active Between 3-5 cm 6 cm
2. Augment with oxytocin as long as labor
there is no evidence of fetal Rate of
Nullipara: >1.2 cm/hr Nullipara: 0.5-0.7 cm/hr
distress or obstructed labor cervical
Multipara: >1.5 cm/hr Multipara: 0.5-1.3 cm/hr
dilatation
Rate of Nullipara: >1 cm/hr
Undetermined
descent Multipara: >2 cm/hr
th
95 % for nullipara:
With EA*: 3.6 hrs
Duration of Without EA*: 2.8 hrs
2nd stage
Duration is much
shorter in multiparas
*EA – epidural analgesia

Table 2. Comparison among Friedman, WHO, and Zhang

Friedman’s WHO Zhang’s
Curve Partograph Labor Pattern
Figure 3. Modified WHO Partograph (2006)
To improve labor
management,
F. ZHANG’S LABOR PATTERN To define reduce maternal
25. Zhang et al in 2010 (Multicenter study) To prevent
Purpose normal labor and perinatal
1. Recommended that labor be allowed to continue for premature CS
pattern morbidity/
a longer period of time, before 6 cm dilatation, to mortality due to
reduce the rate of intrapartum and subsequent obstructed labor
repeat CS. Shape of
26. Threshold for active labor: 6 cm instead of 4 cm labor
1. Prolongs the observation period Diagonal straight Exponential
curve Sigmoid curve
2. To reduce the rate of caesarean delivery lines staircase line
(cervical
27. Rate of cervical dilatation: dilation)
1. Nullipara: 0.5-0.7 cm/hr
2. Multipara: 0.5-1.3 cm/hr
28. The 95th percentiles indicate that
1. At 4 cm, it could take > 6 hours to progress to 5 cm
2. At 5 cm, it may take > 3 hours to progress to 6 cm
29. Only after 6 cm did multiparas show faster labor than
nulliparas, which is consistent with the labor curve
30. In the 2nd stage of labor, the 95th percentiles for
nulliparas with and without epidural analgesia were 3.6
hours and 2.8 hours, respectively. The duration of the
2nd stage was much shorter in multiparas
31. Recommended for third-world countries (e.g. Philippines)

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 Active phase
Alert line starts at (2016) (Williams 25E)
4cm Progression is Recommendation in the Management of the 1st
starts at 4cm
slow before Stage of Labor
Progres- Action line is 4hrs 6cm
Accelerates at:  Admonish against CS delivery in the latent phase of labor
sion from alert line
- Nullipara:  Recommends against CS delivery if labor is progressive but
pattern Duration is
1.2cm/hr slow
Cervical dilatation shorter than
- Multipara:
during the active 4hrs after 6cm  Protraction disorder
1.5cm/hr
labor is <1cm/hr  Cervical dilatation threshold that serves to herald active labor is
Validity Validated in a
Historically 6cm (not 4cm)
and multicenter trial Not yet
governs labor  CS delivery for active-phase arrest should be reserved for
Useful- 1990-1991 in validated
management women at or beyond 6cm of dilatation with ruptured membranes
ness SEA
who fail to progress despite 4 hrs of adequate uterine activity, or
G. MATERNAL-FETAL EFFECTS OF DYSTOCIA at least 6 hrs of oxytocin administration with inadequate
Maternal Effects contractions and no cervical change
 Intrapartum infection
 Occurs especially with frequent internal examinations Recommendation in the Management of the 2nd Stage
 Intrapartum and postpartum pelvic infections are more of Labor
common with desultory and prolonged labors  Before 2nd stage labor arrest is diagnosed,
 Postpartum hemorrhage from atony  Allow a nullipara to push for at least 3 hrs
 Increased with prolonged and augmented labors  Allow a multipara to push for at least 2 hrs
 Pathological retraction ring of Bandl  NOTE: maternal and fetal status should be reassuring
 Associated with stretching and thinning of lower uterine
segment (LUS); may be seen as a uterine indentation RECOMMENDATIONS
 Signifies impending rupture of LUS (CPG on Abnormal Labor, POGS, 2009)
 Uterine rupture Prolonged Latent Phase
 Fistula formation  Observation, rest, and therapeutic analgesia or strong
 Pelvic floor injury sedatives are favored over a more active approach of
amniotomy and oxytocin induction
Fetal Effects  CS has no place without other clear indications like CPD &
 Caput succedaneum (focal swelling of the scalp) abnormal FHR pattern
 Cephalohematoma (injury to the periosteum)
 Molding Protracted Active Phase Dilatation
 Amniotomy with early oxytocin augmentation shortens labor
by as much as 2 hrs compared to expectant care
 Oxytocin should be used to achieve adequate contractions (200
MVU) before operative delivery is considered

Arrest Disorders
 If with CPD, do CS
Figure 5. Caput succedaneum (L) and Cephalohematoma (R).  CS delivery is not performed for labor arrest until:
 At least 4 hrs of UC (> 200 MVU) or
II. ABNORMAL LABOR  A minimum of 6 hrs of oxytocin augmentation if the UC
Protraction Disorder pattern could not be achieved
 Slower than normal rate of cervical dilatation or descent  Extending the minimum period of oxytocin augmentation for
 30% with protraction disorders have CPD active phase arrest from 2 hrs to 4 hrs appears effective
 Vaginal delivery is still possible. During protraction, check which
of the power or passenger is “defective.” If neither is defective, Table 3. Abnormal Labor Patterns
do amniotomy. Hindi CS agad! Abnormal Labor
Nullipara Multipara
Patterns
Arrest Disorder Prolongation Disorder
 No progress in cervical dilatation or descent Prolonged latent phase
 45% with arrest disorders have CPD Management: > 20 hrs > 14 hrs
observation
Protraction Disorders
Failure
Protracted active
 Failure of descent phase (max. slope of
dilation) < 1.2 cm/hr < 1.5 cm/hr
Precipitate Labor Management:
 Delivery in < 3 hours (faster delivery) amniotomy/ oxytocin
 May be related to cervical dilatation or descent
 May result in intracranial hemorrhage, atony

OBSTETRIC CARE CONSENSUS COMMITTEE

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 Protracted descent B. TYPES OF UTERINE DYSFUNCTION
(max. slope of descent, < 1 cm/hr < 2 cm/hr Hypotonic Uterus
pelvic division)  No basal hypertonus
Arrest Disorders  Synchronous uterine contraction
Prolonged deceleration  Slight increase in pressure insufficient to dilate cervix
(cervical dilation arrested > 3 hrs > 1 hr
at 8-9 cm)  Management: Augment with oxytocin
Secondary arrest of  Oxytocin is not effective by mouth (thus, IV)
> 2 hrs
dilatation  Each mL = 10 USP units
Arrest of descent  Half-life = 3 minutes
[descent stops during > 1 hr  Preparations:
pelvic division (+1)]
 10 U oxytocin in 1L D5W
Lack of descent during deceleration
Failure of descent phase or 2nd stage of labor (until  Total dose < 10 U
Station 0 only)  Infusion rate not > 30-40mL/min
> 3 hrs with > 2 hrs with  Side Effects of Oxytocin:
regional regional  Cardiovascular
Prolonged 2nd stage analgesia analgesia  IV bolus can cause transient fall in BP with abrupt
increase in CO (that is why we don’t give oxytocin bolus)
> 2 hrs without > 1 hr without
 ECG changes in MI
Precipitate Labor
 Increase in mean pulse rate
Precipitate active
phase (stops at > 5 cm/hr > 10 cm/hr  Water Intoxication
maximum slope phase)  Due to anti-diuretic action
Precipitate descent > 5 cm/hr > 10 cm/hr
Hypertonic Uterus
III. ABNORMALITIES IN POWER (UTERINE  Increased basal tone
DYSFUNCTION)  Pressure gradient distorted
A. NORMAL UTERINE CONTRACTION  Uterine contraction at midsegment > fundus
32. The fundus has the greatest and longest myometrial  Management: Sedate the patient
activity
33. Lower limit of contraction pressure required to dilate the C. UTERINE ACTIVITY
cervix: 15 mmHg 36. Quantified as the number of contractions present in a
34. Normal spontaneous contraction: 60 mmHg 10-minute window, average over 30 minutes
35. Uterine activity where clinical labor starts: 80-120 MVU 37. Normal: ≤ 5 contractions in 10 minutes
38. Uterine Tachysystole: > 5 contractions in 10 minutes,
Montevideo Units (MVU) qualified as to +/- of associated fetal heart rate
 Increase in uterine pressure above the baseline tone in a 10 decelerations
minute period
 Adequate uterine contraction: 200 MVU IV. ABNORMALITIES IN THE PASSENGER
 Inadequate uterine contraction: < 200 MVU A. FACE PRESENTATION
 Diagnosed in 80% of active phase arrest
 MVU = Increase in uterine pressure above baseline tone of a
uterine contraction in mmHg x Uterine contraction frequency per
10 minutes
 Or, as in the example below, add the increases in uterine
pressure above the baseline over a 10-minute period

Figure 7. Face presentation

Description  Presenting Part: Chin/Mentum
 Presenting Diameter:
Submento-bregmatic diameter = 9.5cm
 The occiput is the longer end of the head lever;
the chin is directly posterior
 Neck and back come in contact
 Head is hyperextended
 Occiput is in contact with fetal back
 Problem: If mentum posterior, the brow is
compressed against the maternal symphysis
pubis preventing flexion of the head  CS
Figure 6. Calculating MVUs  If mentum posterior: Cannot be delivered
vaginally except with a very preterm fetus
 If mentum anterior: May still be delivered

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 vaginally depends on the ultimate presentation
Incidence  1:600 or 0.17% (Williams, 24th Ed)
 Vaginal exam: fetal mouth, malar bones,  If brow persists: prognosis is poor for
Diagnosis orbital ridges vaginal delivery unless very small fetus OR
 X-ray: hyperextended head very large birth canal
 Marked enlargement of the neck or coils of  Management is the same as face
cords presentation
 Anencephalic fetus (always face presentation)
Etiology  Contracted pelvis C. TRANSVERSE LIE
 Very large fetus
 Pendulous abdomen
 High parity
 Descent  Internal rotation  Flexion 
Mechanism
Accessory movement of extension  External
of Labor
rotation
 CS is indicated
 No contracted pelvis + effective labor = vaginal
delivery (only applicable to mentum anterior)
Figure 9. Transverse lie. (A) Dorsoanterior (B) Dorsoposterior
 THOM MANEUVER
 Presenting Part: Shoulder
 Convert face to vertex
 Fundal Grip: Empty fundus upon palpation
 NOT RECOMMENDED since it increases
Management  Long axis of fetus perpendicular to the mother
perinatal and maternal morbidity; rarely
successful  Shoulder usually positioned over the pelvic inlet
 Recommended by CPG: Continuous EFM  Head occupies one iliac fossa, and breech
(electronic fetal monitoring) is mandatory due to the other
increased incidence of abnormal FHR pattern  Creates a shoulder presentation
and for fetal compromise  Back may be directed anteriorly or posteriorly
(dorsoanterior or dorsoposterior)
B. BROW PRESENTATION  Side of the mother toward which acromion is
Description directed determine designation of the lie as
right or left acromial
 Neglected transverse lie: A thick muscular
band forming a pathological retraction ring
has developed just above the thin lower uterine
segment. The force generated during a uterine
contraction is directed centripetally at and
above the level of the pathological retraction
ring. This serves to stretch further and possibly
to rupture the thin lower segment below the
Figure 8. Brow presentation retraction ring
 Presenting Part: Eyebrow Incidence  0.3%
 Presenting diameter:  Abdomen is unusually wide
Vertico-mental diameter = 13.5 cm Diagnosis  No fetal pole detected in the fundus
 Fetal head between orbital ridge and  Ballotable head in iliac fossa
Description  Unusual relaxation of the abdominal wall -may
fontanel → delivery can’t take place
 Rarest; unstable presentation (military position) be due to multiparity
 Fetal head occupies a position midway  Preterm fetus
between full flexion and extension Etiology  Placenta previa
 Abdominal exam: chin and occiput can be  Abnormal uterus
palpated  Polyhydramnios
Diagnosis
 Vaginal: front sutures, eyes, orbital ridges, root  Contracted pelvis
of nose, large anterior fontanel can be felt Course of  Spontaneous delivery impossible
Etiology  Same as face presentation Labor  CS required
Mechanism  Engagement is impossible - the caput  Except:
of Labor succedaneum is over the forehead  Conduplicato corpore (fetus doubled upon
Management  Expectant management for spontaneous itself)
conversion to vertex or face  Head and thorax pass through pelvic
 As long as with reassuring FHR and normal cavity at the same time
progress of cervical dilatation and fetal head  Condition that occurs during birth if the
descent fetus is quite small and the pelvis is large
 CONTRAINDICATED: Forceps, manual
conversion
 In transient brow presentations, prognosis

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  Vaginal or forceps delivery
 With effective contractions, adequate flexion of
the head, and a fetus of average size, occiputs
rotate promptly as soon as they reach the
pelvic floor

F. SHOULDER DYSTOCIA

Figure 10. Conduplicato corpore

 IUFD (kasi dead na yung baby to begin with)
 CS is indicated
 External version before or during early labor if
Management
membranes are still intact and no other
complications may be attempted Figure 13. Shoulder dystocia
 Anterior shoulder against symphysis pubis
D. COMPOUND LIE  Incidence increased due to bigger babies
(usually in multiparity patients; babies are
proportionally big)

Maternal fetal consequences:

 Post-partum hemorrhage
 Transient brachial plexus palsies
 Clavicular and humeral fractures
Risk factors:
 Obesity
Description  Diabetes
Figure 11. Compound lie  Multiparity
 Extremity prolapses alongside the presenting ACOG (1997-2000)
part 1. Most cases can’t be predicted or prevented
because there are no accurate methods to
 The left hand is lying in front of the vertex
identify which fetus will develop this
 With further labor, the hand and arm may complication
retract from the birth canal, and the head may 2. UTZ measurements to estimate macrosomia
Description then descend normally have limited accuracy
 If it fails to retract and if it appears to prevent 3. Planned CS delivery based on suspected
descent of the head, the prolapsed arm macrosomia is not reasonable
4. Planned CS delivery may be reasonable
should be pushed gently upward and the
for nondiabetic with EFW > 5kg or diabetic with
head simultaneously downward by fundal fetus EFW > 4.5 kg
pressure.  Initial gentle attempt at traction assisted by
Incidence 1:700 - 1000 Management maternal expulsive effort is recommended +
large episiotomy and adequate analgesia
E. PERSISTENT OCCIPUT POSTERIOR
Maneuvers for Shoulder Dystocia
1. Moderate Suprapubic Pressure
 Most frequently used, very effective
 Downward traction is applied to the fetal head while
suprapubic pressure is applied by an assistant
 Anterior shoulder is thus either depressed or rotated, so the
shoulders occupy the oblique plane of the pelvis and the
Figure 12. Persistent occiput posterior anterior shoulder can be freed
Description  Presenting part: Occiput/Posterior fontanel
 Vertex position
 Chin and thorax in contact
 Baby’s face is facing up instead of down
 1st & 2nd stage of labor are prolonged
 Precise reasons for failure of spontaneous
rotation is unknown Figure 14. Moderate suprapubic pressure
 Painful labor (severe)
 Generous episiotomy is indicated 2. Delivery of Posterior Shoulder
 Occiput has to rotate 135 degrees instead  Carefully sweeping the posterior arm of the fetus across its
of 90 or 45 degrees thru symphysis chest, followed by delivery of the arm

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  Shoulder girdle is then rotated into one of the oblique Figure 19. Hand is placed behind the posterior shoulder of the fetus. The
diameters of the pelvis with subsequent delivery of the shoulder is then rotated progressively 180 o in a corkscrew manner so that
anterior shoulder the impacted shoulder is released (Williams 25E).

8. Rubin Maneuver
 The more easily accessible fetal shoulder is pushed toward
the anterior chest wall of the fetus (arrow)
 Most often, this results in abduction of both shoulders,
reducing the shoulder-to-shoulder diameter and freeing the
impacted shoulder
Figure 15. Delivery of posterior shoulder

3. Symphysiotomy
 Surgical procedure in which the cartilage of the pubic
symphysis is divided to widen the pelvis allowing childbirth
when there is a mechanical problem
Figure 20. Rubin maneuver

9. Zavanelli Maneuver
 The first part of the maneuver consists of returning the head
to the occiput anterior or posterior position.
 The operator flexes the head and slowly pushes it back into
Figure 16. Symphysiotomy the vagina, following which cesarean delivery is performed

4. Deliberate Fracture of Clavicle

 Using the thumb to press the clavicle toward and against the
pubic ramus can be attempted to free the shoulder impaction
difficult in practice

5. Cleidotomy
Figure 21. Zavanelli maneuver
 Cutting the clavicle with scissors

10. Hibbard Maneuver

6. McRobert’s Maneuver
 Pressure is applied to the fetal jaw and neck in the direction
 Pelvic outlet increases by 1.5-2 cm
 Removing legs from stirrups and sharply flexing them onto of the maternal rectum, with strong fundal pressure applied
the abdomen by an assistant as the anterior shoulder is freed

Figure 22. Hibbard maneuver

Figure 17. McRobert’s maneuver

Figure 18. McRobert’s Drills for Shoulder Dystocia

maneuver. Remove the 1. Call for help
legs from the stirrups and 2. Generous episiotomy
sharply flexing the thighs
3. Moderate suprapubic pressure/ Mazzanti Maneuver
up onto the abdomen. The
4. McRobert’s Maneuver
assistant also provides
suprapubic pressure 5. Wood Corkscrew Maneuver
simultaneously (arrow) 6. Delivery of posterior shoulder
(Williams 24E).

7. Wood Corkscrew Maneuver

 Pressure is applied to the anterior aspect of the posterior
shoulder and an attempt is made to rotate the posterior
shoulder to the anterior position

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 Management Protocol for Shoulder Dystocia 1. With gentle downward pressure to
(ALARMER) the posterior shoulder, the anterior
shoulder may become more
Table 1. Management protocol for shoulder dystocia impacted (with gravity), but will
A Ask for help facilitate the freeing up of the
L Lift/hyperflex leg posterior shoulder (2020 Trans)
39. McRobert’s Maneuver 2. Appears to increase the effective
1. Orients the symphysis pubis more pelvic dimensions, allowing fetal
horizontally position to shift  may disimpact the
2. Increase pelvic outlet by 1.5-2 cm shoulders (Lecture)
A Anterior shoulder disimpaction
40. Abdominal approach: Mazzanti
Maneuver
1. Suprapubic pressure applied with
the heel of clasped hands from the
posterior aspect of the anterior
shoulder to dislodge it

Figure 23. Mazzanti maneuver Figure 26. Gaskin maneuver

41. Vaginal approach: Rubin Maneuver
1. Shoulder is pushed down to the G. FETAL MALFORMATIONS
chest 44. Hydrocephalus
R Rotation of posterior shoulder 45. Abdominal tumors
42. Wood Corkscrew Maneuver 1. Wilms tumor
Step 1: Abduction of posterior shoulders 46. Cystic hygroma
47. Conjoined twins

V. ABNORMALITIES IN THE PASSAGES

A. PELVIC INLET

Step 2: Counterclockwise rotation

Figure 27. Pelvic inlet

Level Level of symphysis pubis
Description Anteroposterior diameter (TOD)
48. True/Anatomic Conjugate
(TC/AC)
Normal:
1. Upper margin of pubic
Figure 24. Wood corkscrew maneuver > 11cm
sacral promontory
M Manual removal of posterior shoulder
2. TC = DC – 1.2 cm
E Episiotomy
49. Obstetric Conjugate (OC)
1. Shortest of the pelvic
inlet
2. Shortest distance
Normal:
between sacral
10cm
promontory and
midportion of
symphysis pubis
Figure 25. Midline (L) and mediolateral (R) episiotomy 3. OC = DC – 1.5 to 2 cm
R Roll over onto “all fours” position 50. Diagonal Conjugate (DC) Normal:
43. Gaskin Maneuver 1. Can be measured > 11.5

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 clinically to tip of sacrum
2.From lower margin of
cm
pubis to sacral 61. Post-Sagittal Diameter
promontory Normal:
Abnormalit Contracted pelvic inlet < 7.5 cm
y 51. OC < 10 cm
52. DC < 11.5 cm 62. Transverse Diameter
1. Between inner ridges Normal:
B. PELVIC MIDPLANE of ischial tuberosity 11cm

Figure 28. Pelvic midplane

Level Level of ischial spine
Description 53. Interspinous Diameter
(IS) Normal:
1. Shortest diameter of 10.5 cm
the whole pelvic cavity
54. Anteroposterior
Normal:
Diameter
11. 5cm
55. Post-Sagittal Diameter Normal:
(PS) 4.5 cm
1. Between sacrum and (IS+PS =
a line created by IS 15 cm)
56. Transverse Diameter
1. Between linea Normal:
terminalis 13.5 cm
2. Largest diameter
Abnormalit Contracted midpelvis
y 57. IS < 8 cm
58. IS + PS  13.5 cm
59. Suggest contraction
1. Spines are prominent
2. Pelvic sidewalls converge
3. Narrow sacrosciatic notch

C. PELVIC OUTLET

Figure 29. Pelvic outlet

Level Level of ischial tuberosity
Description Consists of approximately 2 triangular areas
having a common base
60. Anteroposterior Normal:
Diameter 9.5 to
1. Lower margin of pubis 11. 5cm

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