Maternal vitamin D intake during pregnancy and risk of asthma and wheeze in children: a systematic review and meta-analysis of observational studies.

Aims: To summarize the relationship between vitamin D and infant asthma or wheeze.Materials and methods: We used PubMed and Embase to search articles through July 2017 with selection criteria for relevant studies. Random-effect models were used to pool the results of included studies.Results: Ten articles with 14 independent reports of 2073 incident cases of asthma and 1875 cases of wheeze among 23 030 pairs of mother and child were included in our meta-analysis. Compared to those who did not take vitamin D, the mothers who had vitamin D supplementation during pregnancy stage could reduce the risk of asthma or wheeze in infants. The combined odds ratio of infant wheeze was 0.65 (95% CI = 0.54-0.79) and asthma was 0.78 (95% CI = 0.69-0.89). The results almost did not change in the subgroup analyses.Conclusions: It suggests that increasing maternal vitamin D intake during pregnancy might have a protective effect on suffering from wheeze and asthma for children.