The role of cervical length in predicting the success of induction of labour

Abstract

Background. Induction of labour (IOL) is one of the most common procedures conducted in obstetric practice. Several scoring models are used to predict the probability of successful IOL, most notably the modified Bishop score. Cervical length measured by transvaginal ultrasound is gaining more attention as a potential measure of success of IOL.

Objective. To assess the role of transvaginal ultrasound measured cervical length (TVS-CL) in predicting the success of IOL.

Methods. A prospective observational study was conducted in the Pretoria Academic Complex. Patients admitted for IOL between 26- and 41-weeks’ gestation were included in the study regardless of indication. Eligible patients had a modified Bishop score and TVS-CL assessed prior to commencing IOL. IOL was conducted with either mechanical methods, medical methods or a combination thereof.

Results. We recruited 150 patients to the study. The modified Bishop score and TVS-CL were highly correlated (r=–0.74; p<0.0001). The receiver operating characteristics (ROC) curve analysis and the area under the curve (AUC=0.671) highlighted the poor accuracy of TVS-CL in predicting the success of IOLr compared with the Bishop score. The mean of the TVS-CL was 29.20 mm, with sensitivity of 51% and specificity of 83%.

Conclusion. TVS-CL is a poor predictor of success of IOL compared with the modified Bishop score. The Bishop score remains valid in a resource-limited setting