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P18.03: The fetal head‐symphysis distance correlates well with fetal head perineum distance on three‐dimensional intrapartum ultrasound

Objectives: To evaluate the predictive value of maternal weight, Bishop score, and sonographically measured cervical length at 37 weeks’ gestation for predicting the risk of intrapartum Cesarean delivery in parous women with prior vaginal delivery. Methods: This prospective observational study recruited parous women with singleton pregnancies with previous vaginal delivery at 37 weeks’ gestation. Transvaginal ultrasound for measurement of the cervical length was performed and the Bishop score was determined by digital examination. The data collected at enrollment included maternal weight, height and age. A regression model was constructed with control for known intraand post-partum confounders. Results: Five hundred twenty women were analyzed; 6 women (1.2%) underwent Cesarean delivery in labor. Based on univariate analysis, the maternal weight at 37 weeks was significantly associated with the risk for intrapartum cesarean delivery in parous women, whereas cervical length, Bishop score, maternal age and height at 37 weeks, epidural anesthesia, labor induction, and birth weight were not associated. Multiple logistic regression demonstrated that only maternal weight at 37 weeks provided a significant contribution in predicting intrapartum cesarean delivery. To predict cesarean delivery in labor, the best cut-off value of maternal weight was 72.4 kg, with a sensitivity of 83.3% and a specificity of 79.8%. Conclusions: Maternal weight at 37 weeks’ gestation independently predicted the risk of intrapartum Cesarean delivery in parous women with prior vaginal delivery. However, the sonographic measurement of the cervical length and Bishop score were not predictive of Cesarean delivery.