Relationship between prenatal and postnatal exposures to folate and risks of allergic and respiratory diseases in early childhood

Background: It is uncertain whether folate is risk or preventive factor for allergic and respiratory diseases. Objective: To determine the relationship between maternal or offspring folate status and subsequent development of allergic and respiratory diseases in early childhood. Methods: In total, 917 mother-child pairs from a prospective birth cohort in South Korea were studied. Data regarding the children's allergic and respiratory outcomes were obtained from standardized questionnaires completed by the mothers at postnatal months 6, 12, and 24. Serum folate levels were measured in the mothers at mid- and late-pregnancy, and in their children at 24 months of age. Atopic biomarkers were measured in the cord blood (CB) and at 24 months after birth. Biomarkers and clinical outcomes were analyzed and compared between the mother-child pairs divided into two groups according to median serum folate status at mid- and late-pregnancy. Results: Serum folate levels during mid-pregnancy were inversely associated with CB eosinophil count (adjusted odds ratio [OR] 0.72, 95% confidence interval [CI], 0.54-0.96) and positively associated with CB interleukin-10 levels (1.47, 1.11-1.94). Maternal folate level above the median value (≥9.5 ng/ml) during mid-pregnancy was associated with a decreased risk for the child of lower respiratory tract infections (LRTIs) at 6 months of age (adjustedOR 0.50, 95% CI 0.28-0.91) and atopic dermatitis (AD) at 24 months (adjustedOR 0.52, 95% CI 0.31-0.88), but not with LRTIs and AD at other ages. Conclusions: A relatively high maternal serum folate level in mid-pregnancy was associated with a decreased risk of LRTIs and AD in early childhood.