Association between maternal cholecalciferol supplementation and offspring atopic eczema
The prevalences of atopic eczema in the intervention group at ages 12, 24 and 48 months were 7.2%, 11.4% and 6.7% respectively, compared with 12.0%, 14.5% and 8.8% in the placebo group. Table 2 shows the OR of atopic eczema at ages 12, 24 and 48 months in offspring whose mothers received 1000IU cholecalciferol vs placebo. In an unadjusted analysis, offspring of mothers who received 1000IU cholecalciferol had a lower risk OR of atopic eczema at age 12 months, 0.57 (95%CI 0.33, 0.98), p = 0.04 compared to offspring of mothers who received placebo; this changed little after adjusting for breastfeeding duration as a covariate. The ORs of atopic eczema in the intervention group compared to the control group at ages 24 and 48 months were 0.75 (0.47, 1.21) p = 0.25, and 0.75 (0.37, 1.50) p = 0.41, respectively, and changed little in models adjusted for breastfeeding (Table 2) or season at birth. Adjusted estimates are presented graphically in Figure 1. Sensitivity analysis stratified by breastfeeding duration demonstrated a reduced risk of atopic eczema at age 12 months in the intervention group in infants who were breastfed for more than one month (OR 0.48 (0.24,0.94), p = 0.03), but not in those who were breastfed for less than one month (OR 0.80 (0.29,2.17), p = 0.66) (Table 3); however, interaction terms between the intervention and breastfeeding duration were not statistically significant at any of the three follow-up ages (p = 0.41, 0.35, 0.13 at ages 12, 24 and 48 months, respectively).
Sensitivity analyses showed no association between maternal late pregnancy serum 25(OH)D and offspring atopic eczema at any age (Supplementary table 3). Examining the SNPs rs12785878 (DHCR7 ), rs10741657 (CYP2R1 ) and rs6013897 (CYP24A1 ) located in genes involved in vitamin D metabolism10, 14, demonstrated no associations with offspring atopic eczema, although there indications of higher ORs for atopic eczema with rs10741657 (CYP2R1 ) at ages 12 and 24 months, OR 1.44 (0.95, 2.18), p = 0.08, and 1.42 (0.98, 2.04), p = 0.06, respectively (Table 4).