“Bishop has left the building”-a randomized controlled trial to determine our modern induction needs

Abstract

To compare the prediction value of full Bishop score to a “modified” Bishop score and cervical length measured by transvaginal sonography in nulliparous patients undergoing induction of labor at term. A prospective randomized controlled trial of patients admitted for labor induction at term at a single tertiary center between January 2019-December 2021. Patients were randomly assigned to one of the following groups: 1) induction based on full Bishop score; 2) induction based on cervical dilation and effacement alone (“modified” Bishop score); 3) induction based on sonographic cervical length measurements. We excluded patients from the final analysis if they were in active labor pre-induction, had a full Bishop score >5, >2 cm dilation or >80% effacement (“modified” Bishop score), or a cervical length< 20 mm, accordingly. The primary outcome was the rate of vaginal delivery. Secondary outcomes included induction to delivery interval, additional labor augmentation, pain assessment, and adverse maternal and neonatal outcomes. The final analysis included 758 patients. Vaginal delivery rate was similar in all three groups (84% vs. 81% vs 83%, P=0.68), along with the need for additional augmentation, and induction to delivery interval (71.4% vs. 72.3% vs. 70.3%, P=0.35, and 25.6±4.9 vs. 26.3±4.4 vs. 25.5±4.8, P=0.26, respectively). There were no significant differences in adverse maternal or neonatal outcomes between the groups. All 3 methods were similar as predictors of induction success (area under the curve 0.611 vs. 0.607 vs 0.615, P=0.023 vs. P=0.019 vs. P=0.017, respectively) with no significant difference between in test properties including sensitivity, specificity, positive and negative predictive values. Visual analogue scores were similar between the 3 tests (P=0.66). In nulliparous patients undergoing induction of labor, evaluating dilation and effacement alone is as efficient as full Bishop score or sonographic cervical length measurement in prediction of vaginal delivery success and induction to delivery interval with no significant difference in pain level.View Large Image Figure ViewerDownload Hi-res image Download (PPT)