The risk of uterine rupture in trial of labor after cesarean in grand multiparous parturients.

BACKGROUND: Previous cesarean delivery is the main risk factor for subsequent uterine rupture. This study aimed to determine whether grand multiparity (≥5th delivery) elevates the risk for uterine rupture in trial of labor after cesarean (TOLAC). STUDY DESIGN: Retrospective study including all TOLACs with vertex presentation, from 2013 to 2024 in a university-affiliated medical center. The study groups were as follows: (1) grand multiparous parturients (current delivery ≥5), (2) parturients at their third-fourth delivery, and (3) parturients at their second delivery. The primary outcome was uterine rupture rate. Secondary outcomes were obstetric and neonatal complications. RESULTS: A total of 8410 TOLACs were recorded during the study period, including 2516 grand multiparous parturients, 2695 women at their third-fourth delivery, and 3199 parturients at their second delivery. Grand multiparous parturients were older (p < 0.001), had higher birthweights (p < 0.001), and had less preterm deliveries (p = 0.003). Induction and augmentation of labor were conducted in 15% and 17% of grand multiparous parturients, respectively, 11.7% and 15.2% in third-fourth deliveries, and 13.9% and 29% in second deliveries (p = 0.001). Incidence of uterine rupture was lowest among grand multiparous women (0.2% for grand multiparous, 0.6% for third-fourth delivery, and 0.9% for second delivery, p = 0.002). A multivariable model adjusted for maternal age, birthweight, induction, and augmentation revealed that grand multiparity was not associated with an increased risk of uterine rupture in TOLAC, compared to both second (adjusted odds ratio [aOR], 0.16; p < 0.01) and third-fourth deliveries (aOR, 0.27; p = 0.014). Re-analysis restricted to women with parity ≥6, compared to lower-parity women, yielded identical results. CONCLUSIONS: Grand multiparity does not appear to be associated with an increased risk of uterine rupture in TOLAC.