Specific airway resistance according to early maternal Vitamin D status during pregnancy in children aged 5 to 6 years old from the FEPED cohort (RESPIFEPED)

<bold>Background:</bold> Maternal vitamin D deficiency is associated with the risk of asthma in the offspring. Randomized controlled trials of vitamin D supplementation from the second trimester of pregnancy have failed to demonstrate a benefit on the development of asthma in children. <bold>Objective:</bold> To evaluate the association between vitamin D plasma concentration in the first trimester (T1) of pregnancy and the value of effective specific airway resistance (sR_eff) in 5 to 6 years old children. <bold>Methods:</bold> This multicenter study included 140 children born from women enrolled in the prospective FEPED cohort. Associations between sReff and maternal vitamin D plasma concentration measured during T1 and third trimester (T3) of pregnancy and in cord blood were assessed. sR_eff was also analyzed according to in utero and postnatal tobacco smoke exposure and the occurrence of an episode of bronchiolitis before 6 months of age. The impact of maternal vitamin D status on interrupter resistance (Rint), bronchiolitis, preschool and school age asthma, and allergen sensitization was also assessed. <bold>Results:</bold> sR_eff values were not associated with maternal vitamin D status in T1. sR_eff was higher for children who had bronchiolitis before six months (85% vs 75% predicted, p=0.026). Preschool asthma was associated with a lower T3 vitamin D concentration (22 vs 31 ng/ml, p=0.039) <bold>Conclusion:</bold> In a cohort of young children, airway resistance and asthma were not associated with early vitamin D deficiency during pregnancy. These results do not argue for an early supplementation for pregnant women to reduce the risk of impaired lung function and asthma in their offspring.