Maternal intake of one-carbon metabolism-related B vitamins and anorectal malformations in the Japan Environment and Children's Study.

The occurrence of anorectal malformations (ARMs) is thought to be reduced with sufficient folate intake. However, there is no apparent evidence. We focused on enzyme cofactors for one-carbon metabolism, including folate (vitamin B9), vitamin B6, and vitamin B12, and explored the association between maternal combined intake of these B vitamins and the risk of ARMs. Using baseline data from a Japanese nationwide birth cohort study between 2011 and 2014, we analysed data of 89,235 women (mean age at delivery = 31·2 year) who delivered singleton live births without chromosomal anomalies. Information on dietary intake was obtained via a food-frequency questionnaire focused on early pregnancy, and used to estimate B vitamin intake. We also collected information on the frequency of folic acid supplement use. ARM occurrence was ascertained from medical records. We identified 43 cases of ARMs diagnosed up to the first month after birth (4·8 per 10,000 live births). In terms of individual intake of the respective B vitamins, high vitamin B6 intake was non-significantly associated with reduced odds of ARMs. Compared with women in the low combined B vitamin intake group, the odds ratio of having an infant with ARMs was 0·4 (95% confidence interval = 0·2, 1·0) in the high intake group (folate ≥400 μg/day, and upper half of vitamin B6 and/or vitamin B12). In conclusion, our cohort analysis suggested an inverse association between the combined intake of one-carbon metabolism-related B vitamins in early pregnancy, and ARM occurrence.