Maternal intake of vitamin D during pregnancy and risk of recurrent wheeze in children at 3 y of age

Abstract

Background: Vitamin D deficiency and asthma are common at higher latitudes. Although vitamin D has important immunologic effects, its relation with asthma is unknown.

Objective: We hypothesized that a higher maternal intake of vitamin D during pregnancy is associated with a lower risk of recurrent wheeze in children at 3 y of age.

Design: The participants were 1194 mother-child pairs in Project Viva-a prospective prebirth cohort study in Massachusetts. We assessed the maternal intake of vitamin D during pregnancy from a validated food-frequency questionnaire. The primary outcome was recurrent wheeze, ie, a positive asthma predictive index (>or=2 wheezing attacks among children with a personal diagnosis of eczema or a parental history of asthma).

Results: The mean (+/-SD) total vitamin D intake during pregnancy was 548 +/- 167 IU/d. By age 3 y, 186 children (16%) had recurrent wheeze. Compared with mothers in the lowest quartile of daily intake (median: 356 IU), those in the highest quartile (724 IU) had a lower risk of having a child with recurrent wheeze [odds ratio (OR): 0.39; 95% CI: 0.25, 0.62; P for trend < 0.001]. A 100-IU increase in vitamin D intake was associated with lower risk (OR: 0.81; 95% CI: 0.74, 0.89), regardless of whether vitamin D was from the diet (OR: 0.81; 95% CI: 0.69, 0.96) or supplements (OR: 0.82; 95% CI: 0.73, 0.92). Adjustment for 12 potential confounders, including maternal intake of other dietary factors, did not change the results.

Conclusion: In the northeastern United States, a higher maternal intake of vitamin D during pregnancy may decrease the risk of recurrent wheeze in early childhood.

FIGURE 1

Unadjusted inverse linear association between maternal vitamin D intake and risk of recurrent wheeze in offspring. The top band of dots (Yes) represents children who developed recurrent wheeze, and the bottom band of dots (No) represents children who did not develop recurrent wheeze. The vertical lines represent percentiles of maternal vitamin D intake.

FIGURE 2

Risk of recurrent wheeze stratified by vitamin D intake. (Groups are split at 400 IU vitamin D for mothers during pregnancy and at 200 IU vitamin D for children at age 2 y.) Odds ratios are adjusted for the 12 factors in multivariate model 2 (see Table 2). In a formal test for interaction, the main effect of maternal vitamin D intake was significant (P <0.001), but the main effect of child vitamin D intake and the interaction term for maternal-child vitamin D intake were not (P > 0.80 for both).