Comparison of Cervical Length Measured by Transvaginal Ultrasonography and Bishop Score in Predicting Response to Labor Induction

Abstract

Background: This study aims to compare the value of the Bishop score and cervical length measurement by transvaginal ultrasonography in predicting active labor within 6 h, induction-to-delivery interval, and the duration of active labor and to estimate the most useful cutoff points for the two methods.

Methods: This is a prospective comparative study of Bishop score and cervical length measured by transvaginal sonography on 62 nulliparous subjects who underwent induction of labor.

Results: The Bishop score of the subjects ranged from two to seven (2-7). The mean Bishop in this study population was 4.37 + 1.23. The mean cervical length in this study was 25.59 + 6.07. Bishop score was highly significant (P value < 0.0001) in predicting active phase of labor as compared to cervical length (P = 0.004). The best cutoff value for Bishop score to predict induction of labor within 6 h was more than 4 with sensitivity of 69% and specificity of 79%. Similarly, best cutoff value for cervical length to predict induction of labor within 6 h was less than or equal to 25 mm with sensitivity of 51% and specificity of 70%. Bishop score was more significant (P = 0.001) in predicting induction-to-delivery interval within 12 h as compared to cervical length (P = 0.01).

Conclusion: The Bishop score was superior in predicting the response to induction as compared to the cervical length measured by transvaginal ultrasonography.

Keywords: Bishop score; Induction active phase interval; Labor induction; Transvaginal cervical length.

Conflict of interest statement

Compliance with Ethical StandardsRonak Khandelwal, Purvi Patel, Dipa Pitre, Tosha Sheth, and Nandita Maitra have no conflict of interest.All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008 (5).

Figures

Fig. 1

ROC curve of Bishop score with active phase labor within 6 h

Fig. 2

ROC curve of cervical length by TVUS with active phase within 6 h