Vitamin D ‍During Pregnancy May Lower Asthma risk in Kids

Updated June 26, 2025
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A new analysis of a 15-year study suggests that taking vitamin D supplements during pregnancy could lead to lower rates of asthma and wheezing in children. The research, stemming from ⁤the Vitamin D Antenatal Asthma Reduction Trial (VDAART), indicates a potential benefit beyond standard prenatal multivitamins.

the review, conducted by investigators at Brigham and Women’s Hospital, ⁢part of the Mass General Brigham system, reinforces the connection between maternal vitamin D levels and respiratory health‍ in offspring. Their findings appeared in the Journal of Allergy and Clinical Immunology.

Scott T. Weiss, associate director of the Channing Division ⁣of Network ‍Medicine ⁤at Brigham and Women’s Hospital and a Harvard medical School professor, emphasized the ‍prevalence of vitamin⁣ D deficiency, especially among pregnant women who don’t take supplements. He ⁤recommends that ⁣pregnant ⁤women consider a daily intake of at least 4400‍ IU of vitamin D3 throughout ⁤their pregnancy, starting⁣ at conception, to ensure they get enough of⁣ this essential nutrient and to support their child’s health.

Vitamin D, obtained through sunlight, diet, or supplements, is vital for bone health and may play a role in autoimmune conditions. The review highlights a link between vitamin D deficiency and childhood asthma and wheezing, common ⁣ailments among young children. Roughly 40% of children experience daily wheezing by age 3, ⁤and 20% are diagnosed with asthma by age 6.

the relationship between vitamin D and childhood asthma has been debated. While observational studies suggest a protective effect from higher vitamin D levels during pregnancy, the⁤ VDAART clinical trial yielded inconclusive results when comparing supplemented and ⁢non-supplemented ⁣groups.

Weiss noted⁤ the⁤ differences between nutrient and drug trials, explaining that nutrient trials compare varying levels of a‍ nutrient, while drug trials compare a drug against no drug.⁤ He added that understanding the role of ⁤a nutrient like vitamin D during pregnancy requires considering the dosage, timing, and baseline levels in the control group.

The original VDAART study enrolled pregnant women with a family history of allergies‍ or asthma ⁤between 10 and 18 weeks of pregnancy. Half received 4400 IU of vitamin D in addition to the 400 IU in their prenatal vitamin, while the other half received placebos.

The‍ initial VDAART results, published in JAMA ‍in 2016, showed ⁢a 20% reduction in asthma at age 3 in the treatment group, but the finding ⁤had borderline statistical importance. Results at age 6, published in the NEJM in⁤ 2020, were even less notable.

“But, when we stratified the results‍ by the vitamin D level in the control group, both of those analyses ‍became significant,” Weiss said. “When you ⁤adjust for baseline vitamin D levels,we see exactly the effect in the observational studies — a 50% reduction in asthma and wheezing.”

Weiss’s‍ group reanalyzed the data, publishing the ⁣age 3 findings in PLoS One in 2017 and the age 6 data ⁣in the American⁢ Journal of Clinical Nutrition in 2023. The latest review summarizes these ⁣studies and genetic findings, strengthening the potential causal link between vitamin D and⁢ asthma. It also suggests⁢ considerations for future research.

what’s next

Weiss suggests a follow-up clinical trial should begin early in pregnancy, supplementing with 6000⁣ IU of vitamin D and focusing on enrolling women of colour. He believes such trials could improve understanding of vitamin D’s impact on pregnancy outcomes and early-life asthma.