Contribution of ultrasonography to the prediction of the induction-delivery interval: The ECOLDIA prospective multicenter cohort study.

INTRODUCTION: To evaluate the ability of preinduction ultrasonographic cervical length to predict the interval between induction and delivery in women at term with a Bishop score of 4 to 6 at induction.

STUDY DESIGN: This multicenter prospective observational cohort recruited 334 women from April 2010 to March 2014. Inclusion criteria were women with singleton pregnancies at a gestational age ≥37 weeks, with no previous caesarean, a medical indication for induction of labor, and a Bishop score of 4, 5, or 6. All women underwent cervical assessment by both transvaginal ultrasound and digital examination (Bishop score). The induction protocol was standardized. The primary outcome measure was the induction-delivery interval. Hazard ratios (HR) and their 95% confidence intervals (95% CI) were used to assess potential predictors.

RESULTS: Mean gestational age at induction was 40.1 weeks, 60.8% of the women were nulliparous, and the cesarean rate was 13.4%. The mean induction-delivery interval was 20.8 h (± 10.6). Delivery occurred within 24 h for 56.9% (n=190) of the women. An ultrasonographic cervical length measurement less than 25 mm (HR=1.50, 95% CI 1.18-1.91, P<0.01) and parity (HR=1.41, 95% CI 1.21-1.65, P<0.01) appeared to predict induction-delivery interval. The cervical length cutoff to reduce the induction-delivery interval was 25 mm.

CONCLUSION: A cervical length cutoff of 25 mm was associated with shorter induction-delivery interval in women at term with a Bishop score of 4 to 6.