Predicting success of induction of labor by comparing transvaginal ultrasonographically assessed cervical factors with Bishop Score

Abstract

Background: Traditionally, the Bishop score as assessed by per vaginal examination, is used to assess the pre-induction favorability of the cervix in predicting the success of induction of labor. However, this assessment is subjective, not reproducible, cannot assess the status of the internal os and membranes when the external cervical os.Transvaginal ultrasonography can assess the supravaginal portion of the cervix, the status of the internal os in a non-laboring cervix, which the Bishop score cannot. This study was undertaken to determine if transvaginal ultrasound, with the objective measurement of the cervical length, could predict the outcome of induction better than clinical assessment obtained by the Bishop score.

Materials and methods:  A single center prospective comparative study was done over a period of 1 year at a tertiary care center among 89 pregnant women who fulfilled the eligibility criteria. After taking a thorough history and general and obstetric examination, Bishop Score is calculated by per vaginal examination and cervical factors like cervical length, are assessed by transvaginal ultrasonography.

Conclusion: Both cervical assessment by TVUS and the Bishop Score successfully predicted outcome of induction of labor .The cervical length as assessed by TVUS is a better predictor of outcome of induction of labor than Bishop Score. Funneling of internal os and the presence of bag of membranes are found to be statistically significant in predicting outcome of induction. Further, the best cut off values for predicting the success of induction for Bishop Score is found to be 4, while that for cervical length is 2.45 cm.