Background
Counselling women for and managing birth after caesarean section are important. Research is needed on evaluation of antenatal factors that predict likelihood of successful trial of labour after caesarean section (TOLAC).

Aim
To evaluate the effect of gestational weight gain on mode of delivery in women having TOLAC.

Materials and methods
A retrospective cohort study of eligible women who underwent TOLAC (January 2012 to July 2015) at a large urban hospital. Gestational weight gain was classified as ‘excessive’ or ‘not excessive’ based on calculated pre‐pregnancy body mass index. Multivariable logistic regression analysis was performed to estimate the association of gestational weight gain and vaginal birth, adjusting for socio‐demographic and pregnancy‐related factors.

Results
Of 534 women, those who gained excessive weight were less likely to have a vaginal birth as women who did not (adjusted odds ratio (aOR) 0.48, 95% confidence interval (CI) 0.29–0.81)). Women with previous vaginal birth were more likely to have a vaginal birth (aOR 3.74, 95% CI 1.90–7.36), while women ≥35, women who had an epidural, and women who delivered at 40 weeks, were less likely (aOR 0.58, 95% CI 0.35–0.97, aOR 0.12, 95% CI 0.07–0.22, and aOR 0.53, 95% CI 0.31–0.91, respectively).

Conclusions
Gaining excessive weight in pregnancy is potentially modifiable, and can be incorporated into individual antenatal counselling, and into risk prediction models, to assist with informed decision making around planned mode of delivery in women with previous caesarean section. Future research could focus on interventions to reduce gestational weight gain in women planning TOLAC.