Presentation on contracted pelvis

www.chitty.com

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

2. 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

3. 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.

4. 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%)

5. 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.

6. VARIATIONS OF FEMALE PELVIS

7. ETIOLOGY OF CONTRACTED PELVIS Nutritional and environmental defects

8. Rachitic flat pelvis Osteomalacic pelvis

9. 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.

10. Naegele’s pelvis

11. Scoliotic pelvis

12. 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.

13. 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.

14. 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.

15. 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.

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

17. 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

18. 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

19. 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

20. 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

21. Abdominal method

22. 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.

23. 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.

24. 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.

25. 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.

26. 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.

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

28. Trail labour

29. 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 .

30. Diagnosis I s 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.

31. 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.