Uterocervical angle: an ultrasound screening tool to predict satisfactory response to labor induction.

A wide uterocervical angle >95° detected during the second trimester was associated with an increased risk for spontaneous preterm birth. We aimed to determine whether an ultrasonographic marker, uterocervical angle, correlates with satisfactory response to labor induction. We conducted a prospective cohort study from May 2016 through December 2017 of singleton term gestations undergoing transvaginal ultrasound for cervical length screening and uterocervical angle measurement. Uterocervical angle was measured between the lower uterine segment and the cervical canal. Latent phase duration >720 min was accepted to be a prolonged latent phase. The primary outcome was a prediction of satisfactory response to labor induction (latent phase duration <720 min). Both anterior uterocervical angle (AUC = 0.802,  < .001) and the cervical length (AUC = 0.679,  < .05) significantly predicted satisfactory response to labor induction. Optimal cutoff value was obtained at the value of 97° (64% sensitivity, 91% specificity) for anterior uterocervical angle and 27 mm (64% sensitivity, 64% specificity) for the cervical length. Kaplan-Meier survival analysis showed that duration from labor induction to delivery was significantly higher in a group with longer cervical length ( = .04), additionally labor induction to delivery time was significantly higher in a group with lower UCA ( = .04). Both the cervical length and anterior uterocervical length were predictors for the satisfactory response to labor induction, and both parameters were found to be significantly associated with time from induction to delivery in survival analysis.