Six-Year Follow-up of a Trial of Antenatal Vitamin D for Asthma Reduction
Abstract
This study investigated the long-term effects of prenatal vitamin D supplementation on asthma and recurrent wheeze in children through age 6. A randomized, double-blind trial compared high dose (4400 IU/day) and standard dose (400 IU/day) vitamin D₃ supplementation in pregnant women at risk for having children with asthma. The primary outcome was the incidence of asthma or recurrent wheeze in offspring. Results showed no significant difference between the groups in the incidence of asthma or recurrent wheeze at 6 years (44.7% in the vitamin D group vs. 45.9% in the control group). Secondary outcomes, including eczema, allergic rhinitis, and lung function measures, also showed no significant differences, except for a minor effect on airway resistance. The study concluded that prenatal vitamin D supplementation alone does not prevent asthma or recurrent wheeze in children by age 6, though higher maternal vitamin D levels were associated with modest improvements in lung function.