Research Glimpse: Most cases of asthma are identified and diagnosed in early childhood, suggesting an association between the origin of asthma and fetal development. Early immunomodulation of the fetus or neonate can effect atopic and asthmatic disease development. While a deficiency in maternal vitamin D levels during pregnancy has been linked with the risk of childhood asthma and asthma-related outcomes in children, results of observational studies remain inconclusive. Therefore, the Vitamin D Antenatal Asthma Reduction Trial aimed to study the effect of daily maternal supplementation with vitamin D3 during the second and third trimesters of pregnancy on neonatal immunity.
Using a randomized, double-blind, placebo-controlled clinical trial, cord blood samples from neonates born to mothers supplemented with 4400 IU/d (n=26) or 400 IU/d (n=25) vitamin D3 were measured for immune cell composition, Toll-like receptor (TLR) expression, and cytokine secretion.
Results identified that mothers supplementing with 4400 IU/d of vitamin D3 effectively increased vitamin 25(OH)D levels to sufficiency (>30 ng/mL) and had significantly higher maternal vitamin 25(OH)D3 levels compared with the 400 IU/d group by the third trimester of pregnancy. This resulted in significantly higher cord blood vitamin 25(OH)D levels, as well as longer and heavier babies born in the group that received 4400 IU/d vitamin D3 versus 400 IU/d. Moreover, the neonates of mothers supplemented with 4400 IU/d vitamin D3 had a 2-fold increase in innate cytokine response, a greater than 4-fold increase in IL-17A production in response to T-cell stimulation, and a greater production of the anti-inflammatory cytokine IL-10.
Clinical conclusion: Increased maternal supplementation of vitamin D during fetal development enhances the immune system of the neonate and may result in protection from asthma-related outcomes and complications in early childhood.
Hornsby E et al. J Allergy Clin Immunol. 2017 May 16. [Epub ahead of print]