Grandmultiparity, maternal age, and the risk for uterine rupture—A multicenter cohort study

Introduction: Uterine rupture is a critical complication causing fetal and maternal morbidity and mortality. Data are conflicting regarding whether grandmultiparity (parity ≥ 6) is a risk factor. This multicenter cohort study aimed to determine whether grandmultiparity (parity ≥ 6) poses a risk for uterine rupture in women with no previous cesarean delivery. Material and methods: A multicenter retrospective study of deliveries that occurred between the years 2003 and 2015 in three tertiary medical centers. Deliveries of grandmultiparous women were compared with those of multiparous women (parity 2-5). Women with previous cesarean deliveries were excluded. Multivariable regression modeling was applied to control for possible confounders. Results: A total of 388 784 deliveries of multiparous women with unscarred uteri were recorded during the study period, including 53 965 deliveries of grandmultiparous women and 334 819 deliveries of multiparous women. Grandmultiparous women were significantly older (33.9 ± 5 vs 27.3 ± 5 years; P < 0.0001). Fourteen cases of uterine rupture were recorded in the grandmultiparae group (1 per 3855 labors) vs 41 in the multiparae group (1 per 8166 labors) (odds ratio [OR] 2.07, 95% confidence interval [95% CI] 1.13-3.81; P = 0.030). However, in a multivariable model controlling for maternal age, the association between grandmultiparity and uterine rupture lost its significance (adjusted OR 1.26, 95% CI 0.66-2.41; P = 0.491), and maternal age emerged as an independent predictor of uterine rupture (adjusted OR 1.08, 95% CI 1.04-1.13; P < 0.0001). Additionally, the risk for uterine rupture was elevated in a linear fashion, concomitant with age. Conclusions: Maternal age is a risk factor for uterine rupture. Grandmultiparity does not increase the risk beyond that associated with maternal age.