Associations between intrauterine vitamin D status and atopic outcomes were examined in an extensively characterized maternal-infant cohort.

Of 1537 recruited to the BASELINE prospective birth cohort, 1412 white mothers were included in the analysis of 25-hydroxyvitamin D (25[OH]D) status and atopic disease, and cord 25(OH)D data were available from 1035 infants.

Circulating 25(OH)D was measured in maternal sera at 15 weeks’ gestation and in umbilical cord blood by using a Centers for Disease Control and Prevention–accredited liquid chromatography with tandem mass spectrometry platform. Interview-led questionnaires regarding medical history, environment, and diet and clinical assessments were conducted on day 2 and at 2, 6, 12, 24, and 60 months. Associations with clinically validated atopic disease outcomes (eczema, food allergy, asthma, allergic rhinitis) at 2 and 5 years were examined by using multivariable logistic regression.

Persistent eczema, food allergy, and aeroallergen sensitization at age 2 years were present in 5%, 4%, and 8%, respectively. Asthma and allergic rhinitis at age 5 years were present in 15% and 5%, respectively. Between children with and without atopic conditions, there were no significant differences in distributions of maternal 25(OH)D concentrations (mean: 58.4 [SD: 26.2] and mean: 58.5 [SD: 26.1] nmol/L) at 15 weeks’ gestation and cord concentrations (mean: 35.2 [SD: 17.8] and mean: 35.4 [SD: 18.3] nmol/L). Neither maternal nor cord 25(OH)D nor both considered in a single model were significant predictors of atopic disease in fully adjusted or stratified models.

No association was demonstrated between antenatal vitamin D exposure and validated, prospectively collected measures of childhood atopic conditions.

As described by the authors, randomized controlled trial data have reported a 26% reduction in risk of childhood asthma and recurrent wheeze at age 3 years associated with vitamin D supplementation during pregnancy, suggesting a crucial window of opportunity for vitamin D’s impact on lung maturation. Contributions to the different results in the current study may have included use of an accredited 25(OH)D assay with more reliable results and lower prevalence of asthma and wheezing at 5 years. Differences in associations between randomized controlled trial and cohort data highlight the need for the exploration of genetic variants associated with immunoglobulin E synthesis or vitamin D receptor polymorphisms to distinguish circumstances in which vitamin D status may influence risk of childhood wheezing and atopic conditions.