1.Anterior view of the pelvis

2. Posterior view of the pelvis

3.Superior view of the pelvis

DefinitionThe term 'cephalopelvic disproportion'

implies disproportion between the head of the baby ('cephalus') and the mother's pelvis. Complications can occur if the fetal head is too large to pass thorugh the mother's pelvis or birth canal.

Cephalo-pelvic disproportion exists when the capacity of the pelvis is inadequate to allow the fetus to negotiate the birth canal.

This may be due to a small pelvis, a nongynecoid pelvic formation, a large fetus, or a combination of these factors.

IncidenceAlthough CPD is rare, affecting only one in

250 pregnancies.

causesThe possible causes of cephalopelvic disproportion (CPD)

include: Large baby due to:

Hereditary factors Diabetes Post maturity

Fetal position -         Occipito-posterior position -         Brow presentation -         Face presentation.

Small PelvisAbnormally shaped pelvis

CPD MythsYour partner is tall.You are too short.Your shoe size is too small.You are petite.You and your partner are different races.You are obese and fatty tissue is padding

your pelvis making it more difficult for your baby to fit through.

Cause cont

-         Problems with the Pelvis: Small pelvis. -         A non-gynecoid pelvic formation-         Abnormal shape of the pelvis due to

diseases like rickets, osteomalacia or            tuberculosis. -         Abnormal shape due to previous accidents. -         Tumors of the bones. -         Childhood poliomyelitis affecting the shape

of the hips. -         Congenital dislocation of the hips. -         Congenital deformity of the sacrum or

coccyx.

Cause cont-         Problems with the Genital tractTumors like fibroids obstructing the birth

passage. -         Congenital rigidity of the cervix. -         Scarring of the cervix due to previous

operations like conisation. -         Congenital vaginal septum.

Diagnosis1) Clinical Pelvimetry:This is an assessment of the female pelvis in

relation to the birth of a baby. It is done manually by vaginal examination to examine the pelvis and to assess the size of the pelvis.

The pelvic bones including the sacrum , the sacro-coccygeal joint, the sacro-sciatic notch, the ischial spines, the ilio-pectineal lines and the pubic arch are palpated. The diameter of the pelvis is measured with the index and middle fingers of the hand.

Pelvic inlet:

Obstetrical conjugate ( The line between the narrowest bony points

formed by the sacral promontory and the inner pubic arch )

a) should be 11.5 cm or moreb) should be 2 cm less than the diagonal conjugate

(distance from undersurface of pubic arch to sacral promontory).

The transverse diameter of the pelvic inlet measures 13.5 cm.

Midpelvis ( The line between the narrowest bone points connects the ischial spines) should exceed 12 cm

Pelvic outlet: The distance between the ischial tuberosities

(normally > 10 cm), and the angulation of the pubic arch.

 

Radiological Pelvimetry ( not done nowadays )

Xrays or CT scans are taken of the pelvis in different angles and views and the pelvic diameter measured.

Treatment of Cephalopelvic Disproportion (CPD): If the surgeon is absolutely certain that there

is cephalopelvic disproportion, then a Cesarian section is the only option to deliver the baby. However women who have an average size baby and and an average sized pelvis or even in women in whom vaginal delivery is doubtful, should always be offered a 'trial of labor'.