Vitamin D status during pregnancy and wheezing and asthma during childhood

Background: Maternal vitamin D can have a protective role on child's respiratory health, but the results from prospective studies are still inconsistent. We examined whether maternal circulating vitamin D levels during pregnancy are associated with wheezing and asthma during childhood in a Spanish birth cohort. Methods: Maternal circulating 25(OH)D3 levels were measured during the first trimester of pregnancy. Information on active wheezing (wheezing episodes plus medication), wheezing patterns (early, late-onset, and persistent wheeze), and physician-diagnosed asthma ever was obtained from parental questionnaires administered from 1 to 7 years in new cohorts(N=1964) and from 1 to 9 years in an old cohort(N=294). We treated maternal 25(OH)D3 levels as continuous (ng/ml) and in tertiles: deficient(<20ng/ml), insufficient(20-30ng/ml), and sufficient levels(<30ng/ml). Results: Children exposed to insufficient vitamin D levels during pregnancy had lower odds of being active wheezers at 4 years in the new cohorts (odds ratio=0.63; 95% CI=0.42-0.97), compared with those children exposed to deficient levels. Children exposed to higher levels of maternal vitamin D had lower risk of developing late-onset wheezing in the new cohorts (relative risk ratio=0.97; 0.94-1.00). Results were similar in the old cohort. Children exposed to maternal vitamin D levels above 20ng/ml had lower odds of ever having diagnosis asthma in both cohorts although results did not reach significance. Conclusion: Maternal vitamin D levels above deficiency may be associated with reduced risk of wheezing and asthma in the offspring. Vitamin D dietary interventions can be considered for its potential and substantial general health benefits and its inexpensive costs.