Vitamin D supplementation in pregnancy, prenatal 25(OH)D levels, race, and subsequent asthma or recurrent wheeze in offspring: Secondary analyses from the Vitamin D Antenatal Asthma Reduction Trial

Abstract

Nutrient trials differ from drug trials because participants have varying circulating levels at entry into the trial. We sought to study the effect of a vitamin D intervention in pregnancy between subjects of different races and the association between 25-hydroxyvitamin D3 (25[OH]D) levels in pregnancy and the risk of asthma/recurrent wheeze in offspring. The Vitamin D Antenatal Asthma Reduction Trial is a randomized trial of pregnant women at risk of having children with asthma randomized to 4400international units/d vitamin D or placebo plus 400international units/d vitamin D. Asthma and recurrent wheezing until age 3years were recorded. African American (AA) women (n=312) had lower initial levels of 25(OH)D (mean [SD], 17.6ng/mL [8.3ng/mL]) compared with non-AA women (n=400; 27.1ng/mL [9.7ng/mL], P<.001). No racial difference was found from vitamin D supplementation in pregnancy on asthma/recurrent wheezing in offspring (P for interaction=.77). Having an initial level of greater than 30ng/mL and being randomized to the intervention group was associated with the lowest risk for asthma/recurrent wheeze by age 3years compared with having an initial level of less than 20ng/mL and receiving placebo (adjusted odds ratio, 0.42; 95% CI, 0.19-0.91). We did not find differences between AA and non-AA mothers in the effect of maternal vitamin D supplementation and asthma/recurrent wheeze in offspring at 3years. Maternal supplementation of vitamin D, particularly in mothers with initial 25(OH)D levels of greater than 30ng/mL, reduced asthma/recurrent wheeze in the offspring through age 3years, suggesting that higher vitamin D status beginning in early pregnancy is necessary for asthma/recurrent wheezeprevention in early life.