Background: Folic acid supplement use during pregnancy might affect childhood respiratory health, potentially mediated by methylenetetrahydrofolate reductase polymorphism C677T (MTHFR-C677T) carriership.
Objectives: We examined the associations of maternal folic acid supplement use and folate, vitamin B 12 and homocysteine concentrations during pregnancy with childhood lung function and asthma.
Methods: This study was embedded in a population-based prospective cohort study among 5653 children. Folic acid supplement use was assessed by questionnaires. Folate, vitamin B 12 and homocysteine plasma concentrations were measured in early pregnancy and at birth. At age 10 years, forced expiratory volume in 1 second (FEV 1 ), forced vital capacity (FVC), FEV 1 /FVC, forced expiratory flow between 25% and 75% (FEF 25-75 ), at 75% of FVC (FEF 75 ), and asthma were examined.
Results: Maternal folic acid supplement use during pregnancy was associated with higher childhood FEV 1 and FVC and with a lower FEV 1 /FVC, compared with no folic acid supplement use. Among mothers carrying MTHFR-C677T variants, preconceptional start of folic acid supplement use was associated with lower FEV 1 /FVC (-0.17 [-0.32, -0.02]) and FEF 25-75 (-0.24 [-0.40, -0.07]). Among children carrying MTHFR-C677T wild-type, a higher vitamin B 12 level at birth was associated with a lower FEV 1 (-0.07 [-0.12, -0.01]) and FVC (-0.09 [-0.15, -0.04]). Folate and homocysteine concentrations were not consistently associated with lower childhood lung function or asthma.
Conclusions: Preconceptional start of maternal folic acid supplement use and higher vitamin B 12 concentrations at birth might adversely affect childhood lung function depending on MTHFR-C677T carriership. The clinical implications need to be evaluated.
(© 2017 John Wiley & Sons Ltd.)