Measurement of obstetric conjugate by ultrasonic tomography and its significance

OBJECTIVE: The purpose of this study was to investigate the clinical usefulness of the measurement of ultrasonic obstetric conjugate. STUDY DESIGN: In 209 pregnant women, ultrasonic obstetric conjugate was measured twice at 28 and 36 weeks of pregnancy. In 26 of these patients the measurement of obstetric conjugate by x-ray pelvimetry was also performed at 36 weeks of pregnancy because of medical indications. Obstetric outcome was investigated in association with ultrasonic obstetric conjugate. The relationship between ultrasonic obstetric conjugate and x-ray pelvimetry was investigated. RESULTS: Ultrasonic obstetric conjugate ranged from 10.7 to 15.1 cm. in 12 patients (5.7%) ultrasonic obstetric conjugate was less than 12 cm. Six of them (50.0%) underwent cesarean section because of dystocia. This percentage was significantly higher than 7.1% of the cesarean section rate (14 of 197) in patients with ultrasonic obstetric conjugate more than 12 cm (P < .001). A close positive correlation was observed between ultrasonic obstetric conjugate and x-ray pelvimetry (r = 0.91; P < .0001). CONCLUSIONS: We conclude that ultrasonic obstetric conjugate measurement is a safe and useful procedure in the prediction of dystocia.