Folic acid supplements in pregnancy and early childhood respiratory health

Background: Folate supplementation is recommended for pregnant women to reduce the risk of congenital malformations. Maternal intake of folate supplements during pregnancy might also influence childhood immune phenotypes via epigenetic mechanisms. Objective: To investigate the relationship between folate supplements in pregnancy and risk of lower respiratory tract infections and wheeze in children up to 18 months of age. Methods: In the Norwegian Mother and Child Cohort Study, questionnaire data collected at several time points during pregnancy and after birth on 32 077 children born between 2000 and 2005 were used to assess the effects of folate supplements during pregnancy on respiratory outcomes up to 18 months of age, while accounting for other supplements in pregnancy and supplementation in infancy. Results: Folate supplements in the first trimester were associated with increased risk of wheeze and respiratory tract infections up to 18 months of age. Adjusting for exposure later in pregnancy and in infancy, the relative risk for wheeze for children exposed to folic acid supplements in the first trimester was 1.06 (95% CI 1.03 to 1.10), the relative risk for lower respiratory tract infections was 1.09 (95% CI 1.02 to 1.15) and the relative risk for hospitalisations for lower respiratory tract infections was 1.24 (95% CI 1.09 to 1.41). Conclusions: Folic acid supplements in pregnancy were associated with a slightly increased risk of wheeze and lower respiratory tract infections up to 18 months of age. The results suggest that methyl donors in the maternal diet during pregnancy may influence respiratory health in children consistent with epigenetic mechanisms.