Induction of labor in women with a scarred uterus: does grand multiparity affect the risk of uterine rupture?

Background: Previous cesarean delivery is the most important risk factor for subsequent uterine rupture. Data are inconsistent regarding grand multiparity (≥6th delivery) and a risk for uterine rupture. Specifically, no data exist regarding the risk that is associated with labor induction or augmentation in grand multiparous women after cesarean delivery. Objective: This study aimed to examine whether grand multiparity elevates the risk for uterine rupture in trials of labor after 1 previous cesarean that involved induction or augmentation of labor. Study Design: A retrospective multicenter study was conducted that included all trials of labor after cesarean delivery at 24–42 gestational weeks with vertex presentation between the years 2003–2015. The study groups were defined in the following manner: (1) grand multiparous parturients (current delivery ≥6) who underwent labor induction or augmentation; (2) multiparous parturients (delivery 2–5) who underwent induction or augmentation; (3) grand multiparous parturients with no induction or augmentation of labor. The primary outcome was uterine rupture rate, which was defined as complete separation of all uterine layers. Secondary outcomes were obstetric and neonatal complications. Results: A total of 12,679 labors were included in the study. The study group included 1304 labors of grand multiparous parturients after 1 previous cesarean delivery, of which 800 parturients underwent induction of labor and 504 parturients received labor augmentation. The multiparous group included 3681 parturients with either labor induction or augmentation. The third group included 7694 grand multiparous parturients without induction or augmentation. Incidence of uterine rupture was similar among the 3 study groups (0.3%, 0.3%, and 0.2%, respectively; P=.847). In the multivariable model that was adjusted for maternal age, ethnicity, diabetes mellitus, birthweight, and prolonged second stage of labor, no association was found between grand multiparity and uterine rupture in women with a scarred uterus who underwent labor induction or augmentation. Conclusion: Labor induction/augmentation during trial of labor after cesarean delivery in grand multiparous parturients appears to be a reasonable option that has a similar uterine rupture risk as in multiparous parturients. Avoiding a mandatory cesarean delivery enables reduction of the risk for future multiple cesarean deliveries.