Combination of ultrasound pelvimetry and fetal sonography in predicting cephalopelvic disproportion.

OBJECTIVE

To assess a method of antepartum diagnosis of cephalopelvic disproportion by comparing the diameters of fetal head with those of the maternal midpelvis.

METHODS

Transvaginal ultrasound pelvimetry was performed on 190 healthy primigravidas with cephalic presentation at 28-35 weeks of gestation, and the fetal heads were measured within one week before delivery. The cephalopelvic indices of diameter, circumference and area were calculated and compared.

RESULTS

The index exhibiting the highest degree of accuracy (77.9%) was the cephalopelvic index of diameter (CID) defined as the difference between the mean diameter of the midpelvis and the fetal biparietal diameter (BPD). Eighty-three percent of the cases with CID less than 15.8 mm needed operative delivery, and 76.2% of the cases with CID more than 15.8 mm underwent vaginal delivery.

CONCLUSIONS

The CID may be used to identify cephalopelvic disproportion before the labor and help obstetricians choose the most appropriate form of delivery in an uncomplicated vertex presentation.