PA30 The modifying effect of maternal body mass index on the influence of maternal vitamin D supplementation on offspring risk of atopic eczema

Abstract

Abstract We recently published evidence from a randomized controlled trial of the protective effect of antenatal cholecalciferol supplementation on the risk of infantile atopic eczema in infants that were breastfed for > 1 month. Reports that cholecalciferol supplementation has a smaller effect on circulating 25-hydroxyvitamin D levels in individuals with a higher body mass index (BMI) led us to examine whether maternal BMI modifies the effect of vitamin D supplementation on offspring atopic eczema in the first 4 years of life. In the Maternal Vitamin D Osteoporosis Study, which was a double-blind, randomized, placebo-controlled trial, mothers were supplemented (from 14 weeks’ gestation until delivery) with cholecalciferol 1000 IU daily or matched placebo. Maternal characteristics, including BMI, were recorded from pre-pregnancy, and offspring atopic eczema was ascertained based on the UK Working Party Criteria for the Definition of Atopic Dermatitis at the age of 12 (n = 636), 24 (n = 611) and 48 (n = 450) months. Mothers and offspring characteristics did not differ between the intervention and placebo groups except for longer breastfeeding duration in the intervention group. Maternal pre-pregnancy BMI was found to modify the effect of intervention on offspring eczema, so associations between maternal cholecalciferol supplementation and offspring eczema were stratified by categories of BMI (< 25, 25–30 and > 30 kg m−2), with findings expressed as odds ratios (ORs). Models were adjusted for breastfeeding duration, and infant sex as sensitivity analysis showed that the intervention had an impact on male infants that were breastfed. As reported previously, the offspring of mothers who received 1000 IU cholecalciferol had lower ORs of atopic eczema at 12 months of age [OR 0.57, 95% confidence interval (CI) 0.33–0.98]; the intervention did not affect the risk of atopic eczema in offspring at 24 and 48 months. Stratified analysis demonstrated reduced odds of atopic eczema at 12 months of age in the intervention group in infants whose mothers had a BMI < 25 kg m−2 (OR 0.28, 95% CI 0.09–0.92) and 25–30 kg m−2 (OR 0.20, 95% CI 0.04–1.06) but not for those with a maternal BMI > 30 kg m−2. The risk of atopic eczema at 24 and 48 months of age in offspring in the intervention group was not modified by maternal baseline BMI, and interaction terms between intervention and BMI were not statistically significant (P > 0.2). These RCT findings support evidence of an attenuated effect of cholecalciferol supplementation in mothers with a higher BMI and point toward potential preventative strategies for offspring eczema where maternal cholecalciferol supplementation can be considered and doses adjusted for BMI.