The document discusses contracted pelvis, including definitions, types, causes, effects on pregnancy and labor, and management. Anatomically, a contracted pelvis has one or more essential diameters shortened by at least 0.5 cm. Obstetrically, it alters normal labor mechanism. Contracted pelvises can be classified as flat, rachitic, osteomalacic, or asymmetrical. Causes include nutritional deficiencies. Effects include slower labor, operative deliveries, and maternal and fetal risks. Management depends on degree of contraction and may include induction, cesarean section, or trial labor.

1. PRESENTATION ON
CONTRACTED PELVIS
Y.NAGAMANI
Msc (N) 2ND YEAR
OBSTESTRICS AND GYNAECOLOGY

6. DEFINITION:
It is indeed difficult to define precisely what constitutes a contracted
pelvis. Anatomically, contracted pelvis is defined as one where the essential
diameters of one or more planes are shortened by 0.5 cm. But of more
importance is the obstetric definition which states 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. Depending upon the degree of contraction,
the head may pass through the pelvis by abnormal mechanism or fail to pass
due to absolute obstruction.
-D.C DUTTA

7. • Anatomical definition: It is a pelvis in which one or more of its
diameters is reduced below the normal by one or more centimeters.
• Obstetric definition: It is a pelvis in which one or more of its
diameters is reduced so that it interferes with the normal mechanism of
labour.

8. Variations of female pelvis
On the basis of the shape of the inlet, the female pelvis is divided into four
parent types:
 Gynecoid (50%)
  Anthropoid (25%)
  Android (20%)
  Platypelloid (5%)

9. • Gynecoid. This is the most common type of pelvis in females and is generally
considered to be the typical female pelvis. Its overall shape is round, shallow, and
open.
• Android. This type of pelvis bears more resemblance to the male pelvis. It’s
narrower than the gynecoid pelvis and is shaped more like a heart or a wedge.
• Anthropoid. An anthropoid pelvis is narrow and deep. Its shape is similar to an
upright egg or oval.
• Platypelloid. The platypelloid pelvis is also called a flat pelvis. This is the least
common type. It’s wide but shallow, and it resembles an egg or oval lying on its
side.

10. VARIATIONS OF FEMALE PELVIS

12. ETIOLOGY OF CONTRACTED PELVIS
• Nutritional and environmental defects

14. Rachitic flat pelvis Osteomalacic pelvis

15. ASYMMETRICAL OR OBLIQUELY CONTRACTED PELVIS
It is seen in (1) Naegele’s pelvis, (2) scoliotic pelvis, (3) due to disease
affecting one hip or sacroiliac joint, and (4) tumors or fracture
affecting one side of the pelvic bones during growing age.

16. Naegele’s pelvis

17. Scoliotic pelvis

18. Robert’s pelvis (transversely contracted pelvis)
This is an extremely rare abnormality. Ala of both the sides are absent
and the sacrum is fused with the innominate bones. Delivery is done by
caesarean section.

19. Mechanism of labor in contracted pelvis with vertex presentation
flat pelvis
 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. The biparietal diameter is thus placed
in the sacrocotyloid diameter (9.5 cm or 8.5 cm) and the narrow bitemporal
diameter is placed in the narrow conjugate. If lateral mobilization is not
possible, there is a chance of extension of the head leading to brow or face
presentation.

20.  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.

25. • 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 callipers.

26. X-ray pelvimetry
• is of limited value in the diagnosis of pelvic contraction or
cephalopelvic disproportion.

27. 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
The Salient Features to be Noted to Detect Contraction at

29. DISPROPORTION
DEFINITION:
• Disproportion, in relation to the pelvis, is a state where the normal
proportion between the size of fetus to the size of the pelvis is
disturbed. The disparity in the relation between the head and the pelvis
is called cephalopelvic disproportion.
D.C DUTTA

30. Cause: 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.
• Pelvic inlet contraction
• Contracted Midpelvis
• Contracted outlet

31. DIAGNOSIS OF CEPHALOPELVIC DISPROPORTION (CPD)
AT THE BRIM
 Clinical (a) Abdominal method; (b) Abdominovaginal (Muller-Munro
Kerr)
 Imaging pelvimetry
• Cephalometry: (a) Ultrasound; (b) Magnetic Resonance Imaging; (c)
X-ray

32. Abdominal method

33. • Abdominovaginal method (Muller-Munro Kerr): This bimanual
method is superior to the abdominal method as the pelvic assessment
can be done simultaneously. Muller introduced the method by placing
the vaginal finger tips at the level of ischial spines to note the descent
of the head. Munro Kerr added placement of the thumb over the
symphysis pubis to note the degree of overlapping.

35. • Degree of disproportion and contracted pelvis: Based on the clinical and
supplemented by imaging pelvimetry, the following degrees of
disproportion at the brim are evaluated
• (1) Severe disproportion: Where obstetric conjugate is < 7.5 cm (3"). Such
type is rare to see.
• (2) 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.

36. EFFECTS OF CONTRACTED PELVIS ON PREGNANCY AND
LABOR
• Pregnancy: The general course of pregnancy is not much affected.
However, the following may occur
• (1) There is more chance of incarceration of the retroverted gravid uterus in
flat pelvis (2) Abdomen becomes pendulous especially in multigravida with
lax abdominal wall (3) Malpresentations are increased three to four times
and so also increased frequency of unstable lie.

37. • Labor: The course of events in labor is greatly modified depending upon the degree of
pelvic contraction and presentation of the fetus
• (1) There is increased incidence of early rupture of the membranes
• (2) Incidence of cord prolapse is increased
• (3) Cervical dilatation is slowed
• (4) There is increased tendency of prolonged labor and in neglected cases, obstructed
labor with features of exhaustion, dehydration, ketoacidosis and sepsis
• (5) There is increased incidence of operative interference, shock, postpartum; and
hemorrhage and sepsis.

38. • 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.

39. MANAGEMENT OF CONTRACTED PELVIS (INLET
CONTRACTION)
 Induction of labour
 Elective caesarean section at term
 Trial labour

42. Trail labour

44. • MACROSOMIA (generalized fetal enlargement): Abnormally large
size baby weighing more than 4 kg is considered macrosomic.
• The causes are: hereditary, race, size of the parents—particularly the
mother (obesity), poorly controlled maternal diabetes and gestational
diabetes, postmaturity, multiparity and male fetus.

45. Diagnosis
Is suspected because of:
• (1) disproportionate increase in uterine size,
• (2) clinically, the fetus is felt big,
• (3) ultrasonographic measurements of fetal BPD, HC, FL and AC are
done to predict the estimated fetal weight.

47. • Fetal hazards are: surprise dystocia due to cephalopelvic disproportion,
shoulder dystocia, brachial plexus injury, asphyxia, birth trauma and
meconium aspiration. Overall perinatal mortality and morbidity are high.
• Maternal hazards include: injury to the maternal soft tissues (vagina,
perineum), PPH and puerperal sepsis. Maternal morbidity is high.