Is there an optimal inter-delivery interval in women who underwent trial of labor after cesarean delivery (TOLAC)?

BACKGROUND: Inter-delivery interval (IDI) has been proven to be a factor associated with adverse maternal and neonatal outcomes. However, the optimal IDI in trial of labor after cesarean delivery (TOLAC) remains unclear. We aimed to investigate the association between IDI and major maternal and neonatal outcomes in women who underwent TOLAC. METHODS: A multicenter, retrospective cohort study including five hospitals was conducted between January 2018 and December 2019 in Foshan, China. This study included 1080 pregnant women with one or two cesarean deliveries who attempted a TOLAC. Data on maternal and neonatal outcomes were collected from the electronic record system. Maternal and neonatal outcomes in different groups of IDI were compared by univariate and multivariable analyses. RESULTS: A short IDI of < 24 months did not show a statistically significant association with uterine rupture in the univariate analysis (P = 0.668). In multivariable analysis, the incidences of postpartum hemorrhage (OR 19.6, 95% CI:4.4–90.9, P < 0.05), preterm birth (OR 5.5, 95% CI:1.5–21.3, P < 0.05), and low birth weight (OR 3.5, 95% CI:1.2–10.3, P < 0.05) were significantly increased in women with an IDI of < 24 months than in those with a normal interval (24–59 months). Infection morbidity (OR 1.8, 95% CI:1.4–7.9, P < 0.05), transfusion (OR 7.4, 95% CI:1.4–40.0, P < 0.05), and neonatal unit admission (OR 2.6, 95% CI:1.4–5.0, P < 0.05) were significantly increased in women with an IDI of 120 months or more than in those with a normal interval. Postpartum hemorrhage (P = 0.062) had a trend similar to that of a significant IDI of 120 months or more. We found no statistically significant difference in maternal and neonatal outcomes between 24–59 months and 60–119 months. CONCLUSIONS: An IDI of less than 24 months or 120 months or more increased the risk of major maternal and neonatal outcomes. We recommend that the optimal interval for women who underwent TOLAC should be 24 to 119 months. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12978-021-01319-0.