Transvaginal ultrasound parameters to evaluate cervical favorability and predict the outcome of induction of labor

Abstract

Objective: To compare the values of transvaginal ultrasound (TVU) and Bishop score (BS) for predicting outcomes of induction of labor (IOL).

Methods: The BS and TVU were assessed before IOL. TVU parameters included cervical length (CL) and E-Cervix comprising the cervical hard ratio (HR) and the mean strain level of internal os (IOS). Study end-points included the duration of the latent phase within 15 or 18 h and delivery within 24 h.

Results: In multivariable logistic regression models, at the first two end-points, the areas under the curve (AUCs) for CL with HR were 0.733 and 0.777, and the AUCs for CL with IOS were 0.754 and 0.787, respectively, The AUC for HR was 0.750 at the third end-point. With receiver operating characteristic (ROC) analysis, the best cut-off value for CL was ≤1.38 cm and that for IOS was ≥0.35. The AUCs of the TVU scoring system by the cut-off values for CL and IOS for the three end-points were 0.784, 0.833, and 0.855, respectively. The predicting values of both methods were better than those of the BS (AUC = 0.672, 0.694, and 0.687, respectively).

Conclusion: Cervical length along with E-Cervix showed better predictive values for successful induction compared with the BS.

Keywords: Bishop score; cervical elasticity; cervix length; induction of labor; ultrasound.