Introduction: Great variations in cesarean rates after induction of labor exist and reasons for these disparities remain unclear. They may be explained by individual characteristics or obstetric practices. Ten-group classification systems have proved their utility to monitor cesarean rates in general population. We aimed to identify groups of women that account for most cesareans after induction of labor using the Nippita reproducible 10-group classification, specifically designed for induced population.
Material and methods: A prospective population-based cohort study was performed in 94 French maternity units, including 3042 women undergoing induction of labor. Women were sorted according to 10 mutually exclusive groups based on parity, weeks of gestation, number of fetuses, fetal presentation and previous cesarean delivery. Relative size, cesarean delivery rate and contribution to the overall cesarean rate were described for each group. Cesarean rates were compared according to the Bishop score at the onset of labor induction. Indications for cesarean delivery were also described in the groups that contributed most to the overall cesarean rate. The MEDIP protocol was registered in ClinicalTrial (NCT02477085).
Results: The overall cesarean rate was 21.0% among this population of induced women. Nulliparous women with a term singleton cephalic fetus (groups 1, 2 and 3; at 37-38, 39-40 and ≥41 weeks of gestation, respectively) accounted for two-thirds of the overall cesarean rate because they were the largest group (relative size of 10.6, 16.6 and 18.1%, respectively) and had higher cesarean rates (27.2, 30.9 and 33.0%, respectively). When the Bishop score was <6 (n = 2270/3042), cesarean delivery rates were higher (24.1 vs 10.7% if Bishop score ≥6, P < 0.01), in particular for group 1 (29.1 vs 12.5%, P = 0.02), and group 2 (33.3 vs 19.3%, P = 0.01). In groups 1, 2 and 3, which contributed most to the overall cesarean rate, a significant part of the cesareans were performed before 6 cm of cervical dilation for dystocia only (40.0, 16.7 and 17.6%, respectively).
Conclusions: Nulliparous women with a term singleton cephalic fetus and an unfavorable cervix represent the population to target for auditing induction practices. Specific actions could be implemented among this population to weigh the benefits and risks of induction and improve the management of labor induction.
Keywords: Bishop score; audit; cesarean; classification; failed induction of labor; induced labor.
© 2019 Nordic Federation of Societies of Obstetrics and Gynecology.