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.