Comparison of transvaginal sonographic cervical length measurement and Bishop score for predicting labour induction outcomes.

Abstract

Induction of labour (IOL) is of increasing prevalence worldwide and reliable prediction of its successful outcome is important. Traditional clinical methods for predicting successful IOL outcomes have been supplemented with newer technologies. The aim of this study was to compare transvaginal sonographic (TVS) cervical length measurement with Bishop score in predicting labour induction outcomes. This study included pregnant women with term pregnancy, indication for IOL and unfavourable cervix (Bishop score >6) who had TVS performed prior to IOL. Exclusion critetia were regular contractions, ruptured membranes, non-cephalic presentation, uterine scar and pregnancy complications potentially influencing study outcomes. Outcomes measured were successful IOL defined as achievement of active phase of labour and vaginal delivery. Receiver operating characteristic (ROC) curves were used to determine diagnostic accuracy and sensitivity, specificity, positive and negative predictive values. Statistical significance was defined as p<0.05. Among 112 studied participants, IOL was successful in 101 (90.2%) pregnant women. AUC for Bishop score >2 was 0.831 (95% CI, 0.744-0.917, p<0.001) and for cervical length <30mm 0.679 (95% CI 0.514-0.844, p<0.052). A total of 81 (72.3%) pregnant women delivered vaginally; AUC for Bishop score >2 was 0.754 (95% CI 0.648-0.861, p<0.001) and for cervical length <30mm 0.602 (95% CI 0.484-0.720, p=0.092) which was the only insignificant predictor. Bishop score >2 is a better predictor for both successful IOL and vaginal delivery among induced women with term pregnancy and unfavourable cervix compared to cervical length <30mm.