Comparison of the accuracy of transperineal ultrasound and Bishop Score in predicting the success of labor induction: a cohort study

BACKGROUND: The increasing trend of labor induction lacks an objective and reliable method for predicting its success. While the Bishop Score has been widely used for such predictions, recent advancements suggest transperineal ultrasound could offer a more accurate prognosis, particularly in nulliparous women. This study assesses the predictive accuracy of Bishop Score versus transperineal ultrasound measurements taken before labor induction.METHODS: In a cohort study design, 47 nulliparous pregnant women who were eligible for labor induction were selected through purposive sampling. Cervical length and head symphysis distance were measured through transperineal ultrasound examination before labor induction. Bishop Score assessment was conducted by evaluating cervical characteristics through vaginal examination.RESULTS: The sensitivity and specificity values of 75 and 36.84 for Bishop Scores, 57.89 and 66.6 for cervical length, and 96.43 and 94.74 for head symphysis distance. Only the head symphysis distance significantly predicted successful labor induction (P<0.001). Regression analysis further confirmed that only cervical length (P=0.039) and head symphysis distance significantly predicted labor induction success (P=0.002).CONCLUSIONS: Transperineal ultrasonography measurements of head symphysis distance and cervical length have higher predictive values for labor induction success compared to the Bishop Score.