Evaluation of the Bishop Score in Comparison With Ultrasonographic Markers in Predicting Successful Induction of Labor

TL;DR

This study compares the Bishop score with a new ultrasound-based score to predict successful vaginal delivery after labor induction, finding the new score more accurate.

Contribution

A novel ultrasound-based composite score for predicting successful labor induction outcomes is introduced and shown to outperform the Bishop score.

Findings

The novel ultrasound-based induction score had a higher AUC (0.891) compared to the Bishop score (0.784) for predicting vaginal delivery.

Clinically relevant cutoffs of the new score provided better sensitivity and specificity balance than the Bishop score.

Abstract

Background

Induction of labor (IOL) is a common obstetric intervention, yet accurately predicting successful vaginal delivery remains challenging. The Bishop score is widely used to assess cervical readiness, although its predictive performance is limited by subjectivity and variability. Recent studies suggest that ultrasound-based or composite scoring systems may improve the prediction of induction outcomes. The objective of this study was to compare, within a prospective cohort of women undergoing labor induction at ≥34 weeks of gestation, the predictive performance of the Bishop score and a novel ultrasound-based composite induction score for the primary outcome of vaginal delivery.

Methods

This prospective observational cohort study included 200 women undergoing IOL at ≥34 weeks of gestation for standard obstetric indications. Prior to induction, all participants underwent digital cervical examination for calculation of the Bishop score and standardized ultrasound assessment. The novel induction score integrated sonographic parameters, including cervical length, fetal head characteristics, cervical elastography, and cervical angulation. The primary outcome was vaginal delivery. Receiver operating characteristic curve analysis was used to assess predictive performance.

Results

The mean maternal age was 30.8 ± 5.4 years, and 56.0% of participants were nulliparous. Vaginal delivery occurred in the majority of cases. The Bishop score demonstrated good predictive ability for vaginal delivery (AUC 0.784, 95% CI 0.686-0.882; p < 0.001). The novel induction score showed significantly higher discriminative performance (AUC 0.891, 95% CI 0.827-0.955; p < 0.001). Clinically relevant cutoffs of the new score provided a more favorable balance between sensitivity and specificity compared with the Bishop score.

Conclusions

While the Bishop score remains a useful baseline tool, the novel ultrasound-based induction score demonstrated superior predictive accuracy for vaginal delivery. These findings suggest that incorporating objective sonographic parameters into pre-induction assessment may improve risk stratification and support individualized clinical decision-making. External validation is warranted before routine clinical implementation.

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