Contracted pelvis, CEPHALOPELVIC DISPROPORTION, PELVIC ABNORMALITY, CPD, TYPES OF PELVIS , TYPES OF PELVIS AND ITS OUT COME, MECHANISM OF LABOUR IN CONTRACTED PELVIS, DIAGNOSIS OF CPD, DIAGNOSIS and MANAGEMENT OF CONTRACTED PELVIS, PELVIMETRY, PELVIC ASSESSMENT, TRIAL OF LABOUR

1. CONTRACTED PELVIS
Dr. M. GOKUL RESHMI
OBG

2. DEFINITION
Anatomical definition:
• The essential diameters of one or more planes are shortened by
0.5 cm.
Obstetric definition:
• Alteration in the size and/ or shape of the pelvis of sufficient
degree as to alter the normal mechanism of labor in an average
size baby.

3. VARIATIONS OF FEMALE PELVIS
• The size and shape of the female pelvis differ widely.
• On the basis of the shape of the inlet, the female pelvis is divided
into four types:
• Gynecoid (50%)
• Anthropoid (25%)
• Android (20%)
• Platypelloid (5%)

4. GYNECOID PELVIS – 50%
• INLET:
• Shape - Round .
• Anterior and posterior segment - Almost equal and
spacious.
• Sacrum - Sacral angle (SA) more than 90°. Inclined
backwards. Well curved from above down and side to side.
• Position - Occipito-lateral or oblique Occipito-anterior.
• Diameter of engagement - Transverse or oblique.
• Engagement - No difficulty, Usual mechanism.

5. GYNECOID PELVIS – 50%
• CAVITY:
• Sacro-sciatic notch - Wide and shallow.
• Sidewalls - Straight or slightly divergent.
• Internal rotation - Easy anterior rotation

6. GYNECOID PELVIS – 50%
• OUTLET:
• Ischial spines - Not prominent.
• Pubic arch - Curved.
• Subpubic angle - Wide (85°).
• Bituberous diameter - Normal.
• Delivery - No difficulty.

7. ANTHROPOID PELVIS – 25%
• INLET:
• Shape – Antero-posteriorly oval .
• Anterior and posterior segment - Both increased with slight
anterior narrowing.
• Sacrum - SA more than 90°. Inclined posteriorly. Long and narrow.
Usual curve.
• Position - Direct Occipito-anterior or posterior
• Diameter of engagement - Anteroposterior
• Engagement - No difficulty except flexion is delayed

8. ANTHROPOID PELVIS – 25%
• CAVITY:
• Sacro-sciatic notch - More wide and shallow.
• Sidewalls - Straight or divergent.
• Internal rotation - Non-rotation common.

9. ANTHROPOID PELVIS – 25%
• OUTLET:
• Ischial spines – Not prominent.
• Pubic arch - Long and curved.
• Subpubic angle - Slightly narrow.
• Bituberous diameter - Normal or short
• Delivery - More incidence of face-to-pubis delivery.

10. ANDROID PELVIS – 20%
• INLET:
• Shape – Triangular/ HEART shaped.
• Anterior and posterior segment - Posterior segment short and
anterior segment narrow.
• Sacrum - Sacral angle less than 90°. Inclined forwards and straight.
• Position – Occipito-lateral or oblique Occipito-posterior.
• Diameter of engagement - Transverse or oblique
• Engagement - Delayed and difficult.

11. ANDROID PELVIS – 20%
• CAVITY:
• Sacro-sciatic notch - Narrow and deep.
• Sidewalls - Convergent.
• Internal rotation - Difficult anterior rotation. Not occurs early
above the ischial spines, chance of arrest.

12. ANDROID PELVIS – 20%
• OUTLET:
• Ischial spines – Prominent.
• Pubic arch - Long and straight.
• Subpubic angle – Narrow.
• Bituberous diameter - Short.
• Delivery - Difficult delivery with increased chance of perineal
injuries.

13. PLATYPELLOID PELVIS – 5%
• INLET:
• Shape -Transversely oval.
• Anterior and posterior segment - Both reduced-flat.
• Sacrum - SA more than 90°. Inclined posteriorly. Short and straight.
• Position – Occipito-lateral.
• Diameter of engagement – Transverse.
• Engagement - Difficult by exaggerated parietal presentation.

14. PLATYPELLOID PELVIS – 5%
• CAVITY:
• Sacro-sciatic notch - Slightly narrow and small.
• Sidewalls - Divergent.
• Internal rotation - Anterior rotation usually occurs late in the
perineum.

15. PLATYPELLOID PELVIS – 5%
• OUTLET:
• Ischial spines – Not prominent.
• Pubic arch - Short and curved.
• Subpubic angle - Very wide (more than 90°).
• Bituberous diameter - Wide.
• Delivery - No difficulty.

16. ETIOLOGY
Common causes of contracted
pelvis are:
• Nutritional and environmental:
minor variation: Common
major variation: Rachitic and
osteomalacic — rare
Effect of walking Effect on lying Reniform shape of
down position the inlet
Rachitic pelvis
Osteomalacic pelvis

17. ETIOLOGY
• Diseases or injuries affecting the
bones :
Pelvis — fracture, tumours,
tubercular arthritis;
Spine — kyphosis, scoliosis,
spondylolisthesis, coccygeal
deformity.
Lower limbs —
poliomyelitis, hip joint disease.
KYPHOTIC PELVIS
SCOLIOTIC PELVIS

18. ETIOLOGY
Development defects :
• Naegele’s pelvis,
• Robert’s pelvis;
• high or low assimilation pelvis.
NAEGELE’S PELVIS
ROBERT’S PELVIS

19. MECHANISM OF LABOR IN CONTRACTED PELVIS
WITH VERTEX PRESENTATION FLAT PELVIS
In THE FLAT PELVIS, the head finds
difficulty in negotiating the brim and
once it passes through the brim,
there is no difficulty in the cavity or
outlet.
GENERALLY CONTRACTED PELVIS:
The shape remains unaltered, but all
the diameters in the different
planes—inlet, cavity and outlet—are
shortened. There is difficulty from
the beginning to the end.
Mechanism of labor in flat pelvis:
• Lateralization of occiput to the sacral bay;
• Engagement of the head by exaggerated
parietal presentation

20. MECHANISM OF LABOR IN CONTRACTED PELVIS
WITH VERTEX PRESENTATION FLAT PELVIS
The head negotiates the brim by the following mechanism:
• The head engages with the sagittal suture in the transverse diameter.
• Head remains deflexed and engagement is delayed.
• If the anteroposterior diameter is too short, the occiput is mobilized to the
same side to occupy the sacral bay.
• If lateral mobilization is not possible, there is a chance of extension of the
head leading to brow or face presentation.

21. MECHANISM OF LABOR IN CONTRACTED PELVIS
WITH VERTEX PRESENTATION FLAT PELVIS
The head negotiates the brim by the following mechanism:
• Engagement occurs by exaggerated parietal presentation so that the super-
subparietal diameter (8.5 cm), instead of the biparietal diameter (9.5 cm),
passes through the pelvic brim.
• Molding may be extreme and often there is an indentation or even a
fracture of one parietal bone. However, the caput that forms is not big.
• Once the head negotiates the brim, there is no difficulty in the cavity and
outlet and normal mechanism follows.

22. DIAGNOSIS OF CONTRACTED PELVIS
• Degree of contracted pelvis is gradually declining , due to an
improved standard of living and of nutrition.
• Now the presence of fetopelvic disproportion either due to
inadequate pelvis or big baby or more commonly a combination of
the both is common.

23. DIAGNOSIS OF CONTRACTED PELVIS
Past History:
• Medical: Past history of fracture, rickets, osteomalacia, tuberculosis of the
pelvic joints or spines and poliomyelitis is to be enquired.
• Obstetrical:
• prolonged - spontaneous or difficult instrumental delivery is suggestive
of pelvic contraction.
• stillborn or early neonatal death or late neurological stigmata following a
difficult labor without any other etiological factor points towards
contracted pelvis.

24. DIAGNOSIS OF CONTRACTED PELVIS
Physical Examination:
• Stature: less than 5 ft is likely to have a small pelvis.
• Stigma: Deformities (congenital or acquired) of pelvic bones, hip
joint, spine.

25. DIAGNOSIS OF CONTRACTED PELVIS
• Dystocia dystrophia syndrome:
• The patient is stockily built with bull neck, broad shoulders and short thighs,
obese with a male distribution of hairs.
• Usually subfertile, having dysmenorrhea, oligomenorrhea or irregular periods
with increased incidence of pre-eclampsia and a tendency for postmaturity.
• Pelvis is of the android type. Occipito-posterior position is common with
tendency for deep transverse arrest or outlet dystocia increased
incidence of difficult instrumental delivery or cesarean section.
• There is a chance of lactation failure.

26. DIAGNOSIS OF CONTRACTED PELVIS
• Abdominal Examination Inspection: Pendulous abdomen, especially in
primigravidae.
• Obstetrical: unengagement of the head before the onset of labor.
Presence of malpresentation in primigravidae gives rise to a suspicion
of pelvic contraction.

27. PELVIMETRY
• Bimanual examination - clinical pelvimetry, commonly done.
• Imaging studies—radio-pelvimetry, computed tomography (CT) and
magnetic resonance imaging (MRI).

28. PELVIMETRY
• Clinical pelvimetry done around 37 completed weeks, but better at the
onset of labour.
• Bladder should be empty.
• Patient in dorsal position
• Under aseptic preparations.
• The following features are to be noted simultaneously:
• (1) State of the cervix;
• (2) To note the station of the presenting part in relation to ischial spines;
• (3) To test for cephalopelvic disproportion in nonengaged head (described later);
• (4) To note the resilience and elasticity of the perineal muscles.

29. PELVIMETRY - The internal examination
• Sacrum - The sacrum may be smooth, short and
well curved, and the sacral promontory usually
cannot be reached or the sacrum may be long or
straight.
• Sacrosciatic notch - The notch is sufficiently wide
so that two fingers can be easily placed over the
sacrospinous ligament covering the notch. The
configuration of the notch denotes the capacity
of the posterior segment of the pelvis and the
sidewalls of the lower pelvis.

30. PELVIMETRY -The internal examination
• Ischial spines — Spines are usually smooth
(everted) and difficult to palpate. They may be
prominent and encroach to the cavity thereby
diminishing the available space in the mid-
pelvis.
• Iliopectineal lines — To note for any breaking
suggestive of narrow fore pelvis (android
feature).

31. PELVIMETRY - The internal examination
• Sidewalls — Normally they are parallel or divergent. They may be
convergent.
• Posterior surface of the symphysis pubis — It normally forms a smooth
rounded curve. Presence of angulation or breaking suggests abnormality.
• Sacrococcygeal joint — Its mobility and presence of hooked coccyx, if any,
are noted.
• Pubic arch — Normally, the pubic arch is rounded and should
accommodate the palmar aspect of two fingers. Configuration of the arch
is more important than pubic angle.
• Diagonal conjugate — It is the distance between the lower border of
symphysis pubis to the midpoint on the sacral promontory.

32. PELVIMETRY
• Subpubic angle:
• The inferior pubic rami are
defined and in female, the
angle roughly corresponds to
the fully abducted thumb and
index fingers.
• In narrow angle, it roughly
corresponds to the fully
abducted middle and index
fingers.

33. PELVIMETRY
• Transverse diameter of the outlet (TDO) — It
is measured by placing the knuckles of the
first interphalangeal joints or knuckles of the
clinched fist between the two ischial
tuberosities. Normally, it accomodates four
knuckles.
• Anteroposterior diameter of the outlet—The
distance between the inferior margin of the
symphysis pubis and the skin over the
sacrococcygeal joint can be measured either
with the method employed for diagonal
conjugate or by external calipers

34. Brim Midpelvis Outlet
• Diagonal conjugate
• Posterior surface of the symphysis pubis
• Iliopectineal line
• Sacrosciatic notch
• Sacrum
• Ischial spines
• Interspinous diameter
• Sacrosciatic notch
• Sidewalls
• Sidewalls
• Sacrococcygeal joint
• Subpubic arch
• Subpubic angle
• TDO

35. DISPROPORTION

36. DEFINITION
• The disparity in the relation between the head and the pelvis is called
cephalopelvic disproportion.
• Disproportion may be either due to an average size baby with a small
pelvis or due to a big baby (hydrocephalus) with normal size pelvis or
due to a combination of both the factors.
• Fetal head is the best pelvimeter.
• Isolated outlet contraction without midpelvic contraction is a rarity.

37. DEFINITION
• Pelvic inlet contraction : the obstetric conjugate is < 10 cm or the greatest
transverse diameter is < 12 cm or diagonal conjugate is < 11 cm.
• Contracted Midpelvis: the sum of the interischial spinous and posterior
sagittal diameters of the midpelvis (normal: 10.0 + 5 = 15.0 cm) is 13.0 cm
or below.
• Contracted outlet: the interischial tuberous diameter is 8 cm or less. A
contracted outlet is often associated with mid - pelvic contraction. Isolated
outlet contraction is a rarity.

38. DIAGNOSIS OF CEPHALOPELVIC
DISPROPORTION (CPD)
Degree of cephalopelvic disproportion at the brim can be ascertained
by the following:
• Clinical — (a) Abdominal method; (b) Abdominovaginal (Muller-
Munro Kerr)
• Imaging pelvimetry
• Cephalometry — (a) Ultrasound; (b) Magnetic Resonance Imaging;
(c) X-ray

39. DIAGNOSIS OF CEPHALOPELVIC
DISPROPORTION (CPD)
ABDOMINAL METHOD:
• The patient is placed in dorsal position
with the thighs slightly flexed and
separated.
• The head is grasped by the left hand.
• Two fingers (index and middle) of the
right hand are placed above the
symphysis pubis keeping the inner
surface of the fingers in line with the
anterior surface of the symphysis
pubis to note the degree of
overlapping, if any, when the head is
pushed downwards and backwards.
Clinical: In a primigravida with nonengagement of the head
even at labor, disproportion should be ruled out.

40. DIAGNOSIS OF CEPHALOPELVIC
DISPROPORTION (CPD)
INFERENCES:
• No disproportion - The head can be pushed down in the pelvis without
overlapping of the parietal bone on the symphysis pubis.
• Moderate disproportion - Head can be pushed down a little but there is slight
overlapping of the parietal bone evidenced by touch on the under surface of the
fingers.
• Severe disproportion - Head cannot be pushed down and instead the parietal
bone overhangs the symphysis pubis displacing the fingers.
Difficult to elicit in deflexed head, thick abdominal wall, irritable uterus and high-
floating head

41. DIAGNOSIS OF CEPHALOPELVIC
DISPROPORTION (CPD)
• ABDOMINOVAGINAL METHOD (Muller-Munro
Kerr):
• The patient is placed in lithotomy position and
the internal examination is done taking all
aseptic precautions.
• Two fingers of the right hand are introduced
into the vagina with the finger tips placed at
the level of ischial spines and thumb is placed
over the symphysis pubis.
• The head is grasped by the left hand and is
pushed in a downward and backward direction
into the pelvis.
• This bimanual method is superior to the
abdominal method.
• Lower bowel is emptied, preferably by enema.
• The patient is asked to empty the bladder.

42. DIAGNOSIS OF CEPHALOPELVIC
DISPROPORTION (CPD)
INFERENCES:
(1) No disproportion - The head can be pushed down up to the level of
ischial spines and there is no overlapping of the parietal bone over the
symphysis pubis.
(2) Slight or moderate disproportion - The head can be pushed down a little
but not up to the level of ischial spines and there is slight overlapping of the
parietal bone.
(3) Severe disproportion - The head cannot be pushed down and instead the
parietal bone overhangs the symphysis pubis displacing the thumb.

43. DEGREE OF DISPROPORTION AND
CONTRACTED PELVIS
Based on the clinical and supplemented by imaging pelvimetry, degrees
of disproportion at the brim are evaluated:
• Severe disproportion: Where obstetric conjugate is < 7.5 cm (3").
Such type is rare to see.
• Borderline: Where obstetric conjugate is between 9.5 cm and 10 cm.
When both the anteroposterior diameter (< 10 cm) and the
transverse diameter (< 12 cm) of the inlet are reduced, the risk of
dystocia is high than when only one diameter is contracted.

44. EFFECTS OF CONTRACTED PELVIS ON
PREGNANCY AND LABOR
Pregnancy: The general course of pregnancy is not much affected.
• There is more chance of incarceration of the retroverted gravid uterus
in flat pelvis;
• Abdomen becomes pendulous especially in multigravida with lax
abdominal wall;
• Malpresentations are increased three to four times and so also
increased frequency of unstable lie.

45. EFFECTS OF CONTRACTED PELVIS ON
PREGNANCY AND LABOR
Labor:
The course of events in labor
is greatly modified depending upon
the degree of pelvic contraction and
presentation of the fetus:
• There is increased incidence of
early rupture of the membranes;
• Incidence of cord prolapse is
increased;
• Cervical dilatation is slowed;
• There is increased tendency of
prolonged labor and in neglected
cases, obstructed labor with
features of exhaustion,
dehydration, ketoacidosis and
sepsis.
• There is increased incidence of
operative interference, shock,
postpartum; and hemorrhage and
sepsis.

46. EFFECTS OF CONTRACTED PELVIS ON
PREGNANCY AND LABOR
Maternal injuries:
• The injuries of the genital tract may occur spontaneously or following
operative delivery.
• There is increased maternal morbidity and mortality.
Fetal hazards:
• Fetal risks are due to trauma and asphyxia.
• The net effect leads to increased perinatal mortality and morbidity.

47. TRIAL LABOR

48. TRIAL LABOR
• Definition: The conduction of spontaneous labor in a moderate
degree of cephalopelvic disproportion, in an institution under
supervision with watchful expectancy, hoping for a vaginal delivery.
• Aims : A trial labor aims at avoiding an unnecessary cesarean section
and at delivering a healthy baby.

49. CONTRAINDICATIONS
(1) Associated midpelvic and outlet contraction;
(2) Presence of complicating factors like elderly primigravida,
malpresentation, postmaturity, post-cesarean pregnancy, pre-
eclampsia, medical disorders like heart disease, diabetes, tuberculosis,
etc.;
(3) Where facilities for cesarean section is not available round the
clock.

50. CONDUCTION OF TRIAL LABOR
• The labor should ideally be spontaneous in onset. But in cases where
the labor fails to start even on due date, induction of labor may be
done.
• Oral feeding remains suspended and hydration is maintained by
intravenous drip. Adequate analgesic is administered.
• The progress of the labor is mapped with a partograph.
• Monitor the maternal health.
• Fetal monitoring is done clinically and/or using EFM.

51. CONDUCTION OF TRIAL LABOR
• If there is failure to progress due to inadequate uterine contraction,
augmentation of labor may be done by amniotomy along with
oxytocin infusion. On no account should the procedure be employed
before the cervix is at least 3 cm (2 fingers) dilated.
• After the membranes rupture, pelvic examination is to be done:
(a) To exclude cord prolapse;
(b) To note the color of liquor;
(c) To assess the pelvis once more and
(d) To note the condition of the cervix including pressure of the presenting part
on the cervix.

52. SUCCESSFUL OUTCOME
Depends on:
(1) Degree of pelvic contraction;
(2) Shape of the pelvis—flat pelvis is better than android or generally contracted pelvis;
(3) Favorable vertex presentation—anterior parietal presentation with less parietal obliquity is
favorable;
(4) Intact membranes till full dilatation of cervix;
(5) Effective uterine contractions and
(6) Emotional stability of the woman.

53. UNFAVORABLE FEATURES
(1) Appearance of abnormal uterine contraction;
(2) Cervical dilatation less than 1 cm per hour in the active phase (protracted active
phase);
(3) Descent of fetal head less than 1 cm per hour (protracted active phase) inspite
of regular uterine contractions;
(4) Arrest of cervical dilatation and nondescent of fetal head in spite of oxytocin
therapy;
(5) Early rupture of the membranes;
(6) Formation of caput and evidence of excessive molding;
(7) Fetal distress.

54. TERMINATION OF TRIAL LABOR
• Spontaneous delivery with or without episiotomy (30%).
• Forceps or ventouse (30%)—Difficult forceps delivery is to be avoided.
• Cesarean section (40%)—Judicious and timely decision for cesarean
delivery is to be taken.
• However, in significant cases, the section is done even before full
dilatation of the cervix, the indication being uterine inertia or fetal
distress.

55. SUCCESSFUL TRIAL
• A trial is called successful, if a healthy baby is born vaginally,
spontaneously or by forceps or ventouse with the mother in good
condition.
• Delivery by cesarean section or delivery of a dead baby,
spontaneously or by craniotomy, is called failure of trial labor.

56. ADVANTAGE OF TRIAL LABORS
(1) It eliminates unnecessary cesarean section electively decided upon;
(2) It eliminates injudicious use of premature induction of labor with its
antecedent hazards;
(3) A successful trial ensures the woman a good future obstetrics.

57. DISADVANTAGES OF TRIAL LABORS
1) Test of disproportion remains unproven when cesarean delivery is done
due to fetal distress or uterine dysfunction;
(2) Increased perinatal morbidity or mortality due to asphyxia or intracranial
hemorrhage when the trial is prolonged and/or ends in difficult delivery;
(3) Increased maternal morbidity due to the effects of prolonged labor
and/or operative delivery;
(4) Increased psychological morbidity when trial ends with a traumatic
vaginal delivery or in cesarean delivery.

58. MANAGEMENT OF CONTRACTED
PELVIS

59. INLET CONTRACTION
• Minor degrees of inlet contraction does not give rise to much
problem and the cases are left to have a spontaneous vaginal delivery
at term.
• The moderate and the severe degrees are to be dealt by any one of
the following:
• Induction of labor
• Elective cesarean section at term
• Trial labor

60. DELIVERY
Induction of labor prior EDC:
• Induction 2–3 weeks prior to the EDC may be considered only in cases with
minor to moderate degrees of pelvic contraction.
• It is not favored nowadays.
• In a selected multigravida with previous history of difficult vaginal delivery,
this method may be considered 2–3 weeks before the date.
• In any case, one should be certain about the fetal gestational age.

61. DELIVERY
Elective cesarean section at term:
This is commonly done. Elective cesarean section at term is indicated in:
(1) major degree of inlet contraction
(2) moderate degree of inlet contraction associated with outlet contraction or
complicating factors like elderly primigravida, malpresentation, post-cesarean
pregnancy, etc.
• If there is no doubt about the maturity of the fetus, the operation is done in
planned way any time during last week of pregnancy.
• In doubtful maturity, investigations are done to ascertain maturity; otherwise
the operation is withheld till the pains start or the membranes rupture,
whichever occurs early.

62. MIDPELVIC AND OUTLET
DISPROPORTION

63. MIDPELVIC AND OUTLET DISPROPORTION
• Isolated outlet contraction without midpelvic contraction is a rarity.
• In practice the midpelvic and outlet contraction are jointly considered
as outlet contraction.
• Cephalopelvic disproportion at the outlet is defined as one where the
biparietal-suboccipito bregmatic plane fails to pass through the
bispinous and anteroposterior planes of the outlet.

64. MANAGEMENT
Unlike inlet disproportion, clinical diagnosis of midpelvic and outlet
disproportion can only be made after the head sufficiently comes down
into the pelvis.
• Elective cesarean section: Contraction of both the transverse and
anteroposterior diameters of the midpelvic plane or minor
contraction associated with other complicating factors is dealt by
elective cesarean section.

65. TO ALLOW VAGINAL DELIVERY
• In uncomplicated cases with minor contraction, vaginal delivery is
allowed under supervision with watchful expectancy.
• Molding and adaptation of the head and “give” of the pelvis may
allow the head to pass through the contracted zone.
• Delivery is accomplished by forceps or ventouse with deep
episiotomy to prevent perineal injuries, especially with narrow pubic
arch.

66. TO ALLOW VAGINAL DELIVERY
• Labor progress should be mapped with a partograph to make an early
diagnosis of dysfunctional labor due to disproportion.
• Oxytocin may be used to augment labor for adequate uterine
contractions.
• If there is no dilatation of cervix or descent of the fetal head after a
period of 2 hours in the active phase of labor, arrest of labor is
considered. Once arrest disorder is diagnosed, cesarean delivery is
the option.

67. CASES SEEN LATE IN LABOR
• It is not an uncommon problem in the developing countries.
• The principles of management rest on:
(i) Cesarean section to avoid difficult forceps;
(ii) Forceps with deep episiotomy;
(iii) Symphysiotomy followed by ventouse or
(iv) Craniotomy if the fetus is dead.

68. Thank you…