Correlation of Mode of Delivery with Ultrasonic Measurement of Obstetric Conjugate

To use ultrasonography to assess obstetric conjugate in pregnant women at term, and to study its relationship
with mode of delivery and birth weight.
Materials & Methods: Hundred women at term, in early labor or admitted for induction of labor, entered the study. Longitudinal
ultrasonic scanning by transabdominal 3.5 MHz curvilinear probe was performed for measurement of obstetric conjugate from a site
most adjacent to pubic symphysis to the sacral promontory. Based on this obstetric conjugate measurement, women were divided into
three groups namely those with obstetric conjugate < 10 cm, 10.1-12 cm, and > 12 cm. Mode of delivery and birth weight was noted.
Mode of delivery and birth weight were correlated with ultrasonic obstetric conjugate. Ordinary least square method and logistic
regression analysis were used for statistical analysis.
Results: The mean age of the women was 26.68 years. The mean obstetric conjugate of the women under study was 11.32 cm and the
mean birth weight of newborns was 3.145 kg. The relation between birth weight of newborns of patients and ultrasound obstetric
conjugate was a linear co-relation with p value < 0.001. The cesarean delivery rate was 58.3%, 5%, and 14% when ultrasonic obstetric
conjugate was < 10 cm, 10.1-12 cm, and >12 cm respectively. The rate of cesarean delivery was higher in patients with ultrasonic
obstetric conjugate < 10 cm as compared to others and the difference was statistically significant (p<0.001).
Conclusion: Ultrasonic obstetric conjugate measurement is a simple, noninvasive and safe method of assessing the anteroposterior
diameter of the pelvic inlet. An ultrasonic obstetric conjugate of less than 10 cm should alert the obstetrician for a possibility of cesarean
delivery