Objective: Parity is a prognostic variable when considering trial of labor after cesarean section (TOLAC). This study aimed to determine whether grandmultiparous patients are at increased risk of poor TOLAC outcomes such as uterine rupture.
Study design: A retrospective cohort was conducted at a single university-affiliated medical center with approximately 10,000 deliveries per year. The study group included women post one cesarean section who attempted TOLAC carrying a singleton fetus in vertex presentation. We divided the cohort into three groups: group 1 - women who had a parity of 1; group 2 - parity of 2-4; group 3 - parity of 5 and above. The primary outcome was successful VBAC. Secondary outcomes included mode of delivery, uterine rupture, and combined maternal and neonatal adverse outcomes. Data were analyzed using Fisher's exact test, Chi-square test, ANOVA, and paired t-test.
Results: Five thousand four hundred and forty-seven women comprised the study group: group 1 - 879 patients, group 2 - 2374 patients, and group 3 - 2194 patients. No significant between-group differences were found in gestational age at delivery. Rates of a successful VBAC were 80.6%, 95.4%, and 95.5%, respectively. Group 1 were more likely to have a failed TOLAC compared to group 2 (OR 5.02, 95% CI 3.9-6.5, p<.001) and group 3 (OR 5.17, 95% CI 4.0-6.7, p<.001). There was no increased risk of failed TOLAC when comparing groups 2 and 3 (OR 1.03; 95% CI 0.8-1.4, p=.89). Operative delivery rate differed significantly between all three groups; 25.1%, 6.2%, and 3.6%, for groups 1, 2, and 3, respectively (p<.001). The rate of uterine rupture was significantly higher in group 1 compared to group 2 (1.02% vs. 0.29% p=.02) and group 3 (1.02% vs. 0.2%, p=.01, respectively). There were no differences between group 2 and group 3 (0.29% vs. 0.2% p=.78).
Conclusions: Grandmultiparity is not associated with an increased risk of uterine rupture during TOLAC.
Keywords: TOLAC; VBAC; cesarean delivery; grandmultiparity; uterine rupture.