Association Between Obstetric Conjugate Diameter Measured by Transabdominal Ultrasonography During Pregnancy and the Type of Delivery

Background: Normal morphological features of the maternal pelvis are an important prerequisite to vaginal delivery.

Objectives: We aimed to evaluate the association between obstetric conjugate diameter (OCD) measured by ultrasonography and the type of delivery, vaginally (V) or by cesarean (C) section.

Patients and Methods: Pelvimetry was performed in 200 primigravid women for fetal cephalic presentation. The OCD was measured twice by transabdominal ultrasonography during 25-30 weeks and 30-35 weeks of pregnancy.

Results: The mean OCD of both sonographies in groups V and C was 125.51± 8.35 mm (105-144.5) and 112.99 ± 8.53 mm (96-134.5), respectively, which was significantly lower in group C (P<0.001). The values of OCD between the first and second measurements were not different significantly (P=0.065). C-section was indicated in 65 (32.5%) mothers. The optimal cut-off point for the OCD in the prediction of vaginal delivery was ≥ 119.75 mm, with a sensitivity and specificity of 80% and 78.5%, respectively.

Conclusion: The US measurement of OCD might be an accurate method that almost always remains constant during late pregnancy; it is easy to measure and might be confidentially employed for predicting C-section, but needs more precise studies to be used widely.