Transvaginal ultrasonography of the uterine cervix before induction of labor]

OBJECTIVE: To compare the Bishop score and transvaginal ultrasonographic measurement of cervical length for predicting the mode of delivery following medically indicated induction of labor in term patients. METHOD: The study was conducted prospectively among 134 women who required medically indicated induction of labor. Inclusion criteria were singleton pregnancy, gestational age > or = 37 weeks of amenorrhea, cephalic presentation, and intact fetal membranes. Transvaginal ultrasonography was performed for measurement of the cervical length but the patients were managed without considering this parameter. A receiver-operating characteristic curve was constructed to determine the best cut-of value of cervical length for predicting the risk of cesarean section following induction of labor. RESULTS: Thirty six patients (26.9%) underwent cesarean section and cervical dilatation at time of the cesarean section was < 8 cm in 25 cases. The Bishop score was not predictive for the mode of delivery in this study. In contrast, the cesarean section rate was significantly lower in women with a uterine cervix < 26 mm (18.9 vs 36.6%, p = 0.02). Moreover, the difference has concerned only the cesarean sections performed before 8 cm dilatation (9.5 vs 30.0%, p = 0.002). CONCLUSION: Cervical length measured with transvaginal ultrasonography is a better predictor than the Bishop score for predicting the risk of cesarean section following medically indicated induction of labor.