Effect of early and late prenatal vitamin D and maternal asthma status on offspring asthma or recurrent wheeze.

Background: Childhood asthma developmental programming is complex. Maternal asthma is a strong risk factor for childhood asthma, whereas vitamin D (VD) has emerged as a modifiable prenatal exposure.

Objective: Our aim was to examine the combined effect of early and late prenatal VD status in during pregnancies in women with and without asthma on childhood asthma or recurrent wheeze development.

Methods: We conducted a cohort study using prospectively collected data from the Vitamin D Antenatal Asthma Reduction Trial, a randomized, double-blinded, placebo-controlled VD supplementation trial in pregnant women at high risk of offspring asthma (N = 806 mother-offspring pairs). 25-Hydroxyvitamin-D (25(OH)D) level was measured in early and late pregnancy. Our main exposure was an ordered variable representing early and late prenatal VD sufficiency (25(OH)D level ≥ 30 ng/mL) status during pregnancy in women with and without asthma. The primary outcome was offspring with asthma or recurrent wheeze by age 3 years. We also examined the effect of prenatal VD level on early life asthma or recurrent wheeze progression to active asthma at age 6 years.

Results: Among mothers with asthma versus among mothers with early and late prenatal VD insufficiency, those with early or late VD sufficiency (adjusted odds ratio = 0.56; 95% CI = 0.31-1.00) or early and late VD sufficiency (adjusted odds ratio = 0.36; 95% CI = 0.15-0.81) had a lower risk of offspring with asthma or recurrent wheeze by age 3 years (P = .008). This protective trend was reiterated in asthma or recurrent wheeze progression to active asthma from age 3 to 6 years (P  = .04).

Conclusion: This study implies a protective role for VD sufficiency throughout pregnancy, particularly in attenuating the risk conferred by maternal asthma on childhood asthma or recurrent wheeze development.