Contracted Pelvis & Cephalopelvic Disproportion

Question 1

What are the causes for a contracted pelvis?

Answer 1

PELVIC CAUSES
1- developmental causes
- small gynaecoid
- android
- anthropoid
- flat
2- diseases of the bone
- metabolic: flat rachitic pelvic, osteomalacia triradiate pelvis
- fractures of the pelvic bone
- tumors of the pelvic bone
- diseases: TB

SPINAL CAUSES
1- dorso-lumbar scoliosis
2- lumbar kyphosis
3- spondylolisthesis

LOWER LIMB CAUSES
1- dislocation of femur
2- atrophy of lower limb
3- unilateral fracture of tumor
4- unilateral lower limb disease (poliomyelitis)

Question 2

How can a contracted pelvis be suspected during history taking?

Answer 2

History of:
- prolonged labour ending with C.S or stillbirth
- difficult instrumental delivery
- history suggestive of rickets in childhood: delayed walking, dental hypoplasia, frontal bossing, swelling in wrist & ankle joints, bowing of legs
- history of trauma or disease of pelvis, spine, or lower limbs

Question 3

How is a contracted pelvis suspected by general & abdominal examination?

Answer 3

GENERAL
1- height if < 150cm
2- Abnormal gait
3- stigmata of old Rickets: square head, pigeon chest, costal rosary, spine deformities, bow leg
4- dystrophia dystocia syndrome: muscular appearance, short, obese, male hair distribution -> android pelvis
5- spines -> scoliosis or kyphosis
6- lower limb abnormalities

ABDOMINAL
- malpresentation
- pendulous abdomen
- non engagement of fetal head in last 2 weeks in primagravida

Question 4

How is a contracted pelvis diagnosed by pelvic examination?

Answer 4

1- external pelvimetry
2- internal pelvimetry
3- radiological pelvimetry -> lateral x-ray
4- cephalometry -> US assessment: BPD, OFD, HC
5- cephalopelvis disproportion tests: Pinard’s method or Muller-Kerr’s method

Question 5

When should cephalopelvic disproportion tests be done?

Answer 5

In Primigravida with unengaged head after 36 weeks

Question 6

What are the interpretations for the cephalopelvic disproportion tests?

Answer 6

• No disproportion -> head can be pushed into pelvis
• Moderate disproportion (1st degree) -> head doesn’t enter pelvis & is nearly at the level of the anterior surface of the symphysis pubis
• Marked disproportion (2nd degree) -> head overrides the anterior surface of the symphysis pubis -> LSCS

Question 7

What are the maternal complications caused by cephalopelvic disproportion?

Answer 7

• malpresentation
• prolonged labour & slow dilatation of cervix
• PROM & cord prolapse
• ruptured uterus
• PPH
• maternal infection
• necrotic genitourinary fistula

Question 8

What are the fetal complications caused by a contracted pelvis?

Answer 8

• intracranial hemorrhage
• fractures of the skull
• birth injuries
• asphyxia
• cord prolapse
• intra-amniotic infection
• nerve injuries

Question 9

When can a trial of labour be done in a case of cephalopelvic disproportion?

Answer 9

In moderate degree (1st degree cephalopelvic disproportion)
1- young healthy primigravida
2- moderate disproportion
3- vertex presentation
4- no marked outlet contraction
5- no post-maturity
6- Thomas dictum sum > 15cm + bituberous > 8cm + sub-pubic angle not very narrow -> generous episiotomy & low forceps

Question 10

What are the factors that are tested during a trial of labour?

Answer 10

• moulding of head
• asynclitism -> anterior is better than posterior
• yielding of pelvis
• efficiency of uterine contractions
• dilatation of cervix

Question 11

When should the trial of labour be terminated by C section?

Answer 11

• marked uterine inertia
• rigid hanging cervix
• PROM
• fetal head showing marked deflexion or moulding
• fetal or maternal distress

Question 12

What are the indications for C section in contracted pelvis?

Answer 12

• marked disproportion if fetus is living
• moderate disproportion if trial is contraindicated or failed
• markedly contracted outlet
• contracted pelvis in elderly PG
• contracted pelvis associated with complications & placenta Previa