Comparing Pre-Induction Ultrasound Parameters and the Bishop Score to Determine Whether Labor Induction Is Successful

Abstract

Background and Objectives: The incidence of labor induction is steadily increasing worldwide. The main aim of this study was to evaluate the ultrasound parameters and their mutual correlation and to analyze the parameters’ predictive capability in assessing the success of labor induction. The secondary goal was to assess patients’ tolerability and acceptance of transvaginal ultrasound and digital gynecological examination. Materials and Methods: This prospective observational follow-up study included 252 women selected for labor induction. The transvaginal ultrasound examination measured the posterior cervical angle, cervical length, the length and width funneling of the cervix, the distance between the head of the fetus and the external uterine os, and the position of the fetal occiput. After the ultrasound, a digital vaginal examination was performed (according to the Bishop score), and the women were asked to rate their perception of pain for each procedure. Results: The most common indication for labor induction was post-term pregnancy (57.59%), and the most common method of labor induction was oxytocin with amniotomy (70%). The results showed that a significant independent prediction of vaginal delivery could be provided based on the Bishop score and cervical length. Other investigated ultrasound parameters, the length and width of the funneling of the cervix (p < 0.001), the fetal head stage (p < 0.001), and the size of the posterior cervical angle (p < 0.05), showed statistical significance in relation to the success of labor induction. Patients reported lower discomfort and pain during transvaginal ultrasound examination (mean score 2, IQR 3) compared to digital examination (mean score 5, IQR 4), with p < 0.001. Conclusions: The results imply that the assessment of ultrasound parameters before induction of labor is necessary to predict the outcome and reduce the possibility of complications. In terms of tolerability and choice by the patients, the transvaginal ultrasound examination was better rated than the vaginal gynecological examination.