Accuracy of Transvaginal Ultrasound Parameters and Bishop Score as Predictors of Successful Induction of Labor in Term High-Risk Pregnancy.

Background Induction is one of the most common interventions in obstetrics practice, accounting for 1.4-35%. Cervical favorability is crucial for successful induction. The Bishop score is simple and assesses preinduction cervical favorability based on five components. However, it has high inter- and intra-observer variability. Alternative objective methods are transvaginal ultrasound parameters (e.g., cervical length, width, and funneling). Objective To assess and compare the predictive value of transvaginal ultrasound and bishop score for vaginal delivery. In addition, the time interval from induction to delivery in women undergoing induction of labor. Method This prospective cross-sectional study included 342 pregnant women, in whom induction of labor was performed at 38-42 weeks of gestation. Cervical length, funneling, and width from transvaginal sonography and bishop scores by digital examination are assessed prior to induction in high-risk cases according to standard protocol. Result In our study, both transvaginal cervical length and bishop score showed similar predictors of successful labor induction, i.e., vaginal delivery. The ROC curve for cervical length showed an optimal cut-off value of ≤ 32 mm, corresponding to a sensitivity of 64.2% and a specificity of 60.0%, whereas the optimal cut-off value for Bishop score was ≥ 5, with a sensitivity of 65.1% and a specificity of 62.0%. However, cervical width and the presence of cervical funneling did not correlate. Both cervical length and Bishop score had a significant correlation as predictors of successful induction, with an OR of 0.93 (95% CI 0.91-0.96), an AOR of 0.96 (955 CI 0.9-0.99), and an OR of 1.41 (95% CI 1.2-1.6) and an AOR 1.2 (95% CI 1.1-1.5), respectively. Conclusion Cervical length and bishop score are both good and equally predict of successful induction of labor.