Prediction of successful trial of labor after cesarean among grand-multiparous women

Purpose: To determine the factors associated with successful trial of labor after cesarean (TOLAC) among grand-multiparous (GMP) women. Methods: A retrospective cohort study was conducted, including all GMP women (≥ 5 deliveries) undergoing TOLAC during 3/2011 and 6/2020, delivering a singleton cephalic newborn. Factors associated with successful vaginal delivery were examined by multivariable analysis. Results: Overall, 381/413 (92.2%) GMP succeeded TOLAC. Maternal characteristics did not differ between TOLAC success and TOLAC failure groups. Previous cesarean delivery characteristics did not differ between study groups. The median number of previous vaginal births after cesarean was 2 [interquartile range 1–4]. Gestational age at TOLAC was lower in the success group (mean 37^1/7 ± 3^6/7 vs. 38^5/7 ± 3^1/7 weeks, p = 0.028). A lower rate of modified Bishop score < 4 was associated with TOLAC success [149 (39.1%) vs. 22 (69%), odds ratio (OR) 95% confidence interval (CI) 0.29 (0.13–0.64), p = 0.001]. The rate of induction of labor was higher in the TOLAC failure group [120 (31.5%) vs. 17 (53%), OR 95% CI 0.40 (0.19–0.83), p = 0.013]. The rate of oxytocin administration was higher in the TOLAC failure group [94 (24.7%) vs. 15 (47%) OR (95% CI) 0.37 (0.17–0.77), p = 0.006]. The duration of rupture of membranes was negatively associated with TOLAC success. Neonatal and maternal adverse outcomes did not differ between study groups. In multivariable logistic regression analysis, only the duration of rupture of membranes and modified Bishop score < 4 were independently associated with TOLAC success [adjusted OR (95% CI) 0.98 (0.96–0.99), p = 0.027 and 0.40 (0.16–0.97), p = 0.044]. Conclusion: TOLAC among GMP has a very-high success rate. Shortening the duration of ruptured membranes is a modifiable factor that may be associated with increased TOLAC success rates.