High dose of maternal folic acid supplementation is associated to infant asthma

Maternal folic acid supplementation had a positive effect on preventing neural tube defects (NTDs), but its effects in infant asthma remained unclear. A hospital-based case–control study was conducted with outpatients between March 2010 and March 2011 including 150 onset infant asthma cases and 212 controls, together with a meta-analysis involving 14 438 participants, was performed. The association between maternal folic acid supplementation and the risk of infant asthma was not significant either in the meta-analysis (OR = 1.06, 95% CI = 0.99–1.14) or in the case–control study (OR = 0.72, 95% CI = 0.37–1.39). However, quantitative analysis of the supplementation dose demonstrated that the risk of infant asthma significantly increased for the infants whose mother were with high-dose supplementation (>72 000 µg•d; OR = 3.16, 95% CI = 1.15–8.71) after adjusting for confounding factors in the case–control study. Meanwhile, the risk of infant asthma significantly decreased for the infants whose mother were with low-dose supplementation (<36 000 µg•d; OR = 0.36, 95% CI = 0.17–0.77). A high dose of folic acid supplementation for mother during pregnancy was associated with an increased risk of infant asthma, whereas supplementation with a relatively low-dose was associated with a decreased risk of infant asthma. These findings should be further investigated in a large population.