Prediction of Outcome of Labour Induction: Comparison of Transvaginal Sonographic Parameters with Bishop Score

Induction of labour (IOL) is a necessary intervention in 20% of pregnancies to prevent maternal or fetal complications. Successful IOL depends on pre-induction cervical status, traditionally assessed using Bishop Score (BS). This study compares the predictive ability of transvaginal sonographic (TVS) parameters like cervical length (CL), posterior cervical angle (PCA), occipital position (OP) compared to BS for successful IOL and vaginal delivery (VD).

This prospective observational study was conducted at tertiary care center, JIPMER, Southern India. A total of 131 primigravidae at 38-42 weeks with singleton vertex presentation underwent IOL werincluded. TVS was used to measure CL and PCA before induction. Induction was primarily achieved using transcervical Foley catheters, prostaglandins, and oxytocin. Outcome measures included achieving active labour (≥ 4 cm dilation) within 24 h, IOL-to-delivery interval (< 48 h), and successful VD.

Successful IOL was achieved in 93.1% of cases, and VD occurred in 79.4%. TVS parameters were superior to BS in predicting outcomes. CL < 2.8 cm and PCA ≥ 110° showed better sensitivity (72.7 and 73.7%) and diagnostic accuracy (79.3 and 77.9%) than BS. PCA ≥ 110° was the single best predictor of VD within 48 h (AUC 0.90, p < 0.001). BS was less sensitive and specific for predicting successful induction or shorter induction-delivery intervals.

Sonographic parameters (CL and PCA) demonstrate higher predictive validity for successful IOL and VD compared to BS. PCA ≥ 110° emerged as the strongest independent predictor for delivery within 4 h, suggesting the utility of TVS in routine pre-induction assessments.