The pathogenesis of congenital diaphragmatic hernia (CDH) is largely unknown; however, vitamin A seems to play a role in diaphragmatic development. Previous, case-control studies reported that maternal dietary vitamin A intake was inversely associated with the risk of CDH. To our knowledge, however, there is no prospective evidence regarding this association. Our aim was to examine whether maternal intake of vitamin A was associated with CDH occurrence. Baseline data, from the Japan nationwide birth cohort study (2011-2014), on 89,658 mothers (mean age at delivery = 31·2 years) who delivered singleton live births, were analysed. We assessed dietary habits using a food-frequency questionnaire focused on the first trimester, and estimated the daily intakes of total vitamin A (retinol activity equivalents), retinol, provitamin A carotenoids, and vegetables. The occurrence of CDH was ascertained from medical records. A total of 40 cases of CDH were documented. The adjusted odds ratio (OR) of CDH occurrence for the high total vitamin A intake category (median = 468 μg/day) was 0·6 (95% confidence interval (CI) = 0·3, 1·2) with reference to the low intake category (230 μg/day). When we restricted to mothers with a pre-pregnancy body mass index of 18·5 to 24·9 kg/m2, vitamin A intake was inversely associated with the risk of their children being born with CDH (OR = 0·5, 95% CI = 0·2, 1·0). Even given the limited number of cases in the study, our findings provide additional evidence to link vitamin A with CDH.