Maternal use of folic acid supplements during pregnancy, and childhood respiratory health and atopy.

Previous studies have suggested possible adverse side-effects of maternal use of folic acid-containing supplements (FACSs) during pregnancy on wheeze and asthma in early childhood. We investigated the association between maternal use of FACSs and childhood respiratory health and atopy in the first 8 yrs of life. Data on maternal use of FACSs, collected during pregnancy, were available for 3,786 children participating in the Prevention and Incidence of Asthma and Mite Allergy birth cohort study. Questionnaire data on children's respiratory and allergic symptoms were collected annually and allergic sensitisation and bronchial hyperresponsiveness (BHR) were measured at 8 yrs of age. No overall (from 1 to 8 yrs of age) associations were observed between maternal use of FACSs and (frequent) asthma symptoms, wheeze, lower respiratory tract infection, frequent respiratory tract infection and eczema. Maternal folic acid use was associated with wheeze at 1 yr of age (prevalence ratio 1.20, 95% CI 1.04-1.39), but not with wheeze at later ages. Pre-natal exposure to FACSs was not associated with sensitisation and BHR. Apart from a small increased risk of early wheeze, we observed no adverse respiratory or allergic outcomes associated with pre-natal FACSs exposure in our study population.