Association between the cervical sliding sign and successful induction of labor in women with an unfavorable cervix: A prospective observational study

Objectives: To evaluate the role of the cervical sliding sign (CSS) in the prediction of the outcome of induction of labor (IOL). Study design: Two-center prospective observational cohort study involving a non-consecutive series of uncomplicated singleton term pregnancies, planned for IOL, with a fetus in cephalic presentation and unfavorable cervix as defined by a Bishop score ≤ 6. The Bishop score was evaluated by transvaginal digital examination and the cervical length and CSS by transvaginal ultrasound. The presence of CSS was defined as the sliding of the anterior cervical lip on the posterior one under gentle pressure of the transvaginal probe. The primary outcome of the study was successful vaginal delivery within 24 h. The secondary outcome was the induction-to-active-labor time. The interobserver agreement for the CSS was also evaluated. Results: Over a period of 12 months, 179 women were included. The CSS was found in 86 (48.0 %) patients and was associated with an increased likelihood of vaginal delivery within 24 h (60/86 or 69.8 % vs 27/93 or 29.0 %, P < 0.001) and a shorter induction-to-active-labor time (954 ± 618 min vs 1416 ± 660 min, P < 0.001). Multivariable regression analysis showed that the CSS was an independent predictor of vaginal delivery within 24 h (aOR 5.37, 95 % CI 2.26–12.75) and shorter induction-to-active-labor time interval (HR 1.81, 95 % CI 1.19–2.74). The interobserver variability based on intraclass correlation coefficient for the CSS was excellent (ICC = 0.90). Conclusion: In women undergoing IOL with an unfavorable cervix, the CSS is associated with a higher frequency of vaginal delivery within 24 h and a shorter induction-to-active-labor time.