In females having insufficiency of vitamin D in the 1^st trimester, a defensive effect of 3^rd trimester prenatal vitamin D sufficiency was noted on the incidence of allergic rhinitis with aeroallergen sensitization at age three and six years.

This study was carried out for exploring the link between prenatal vitamin D sufficiency and allergic consequences in early childhood in the enrolled subjects of the randomized controlled study of prenatal supplementation of vitamin D [Vitamin D Antenatal Asthma Reduction Trial].

The study recruited 414 mother-offspring pairs with the data of offspring aeroallergen sensitization  available at age six years. The link between prenatal vitamin D sufficiency status, based on vitamin D levels estimated in the 1^st  and 3^rd  trimesters, or vitamin D supplementation therapy assignment was compared with the findings of aeroallergen sensitization, eczema, parent-stated allergic rhinitis, total IgE, parent-stated allergic rhinitis with aeroallergen sensitization, sensitization to food, and any sensitization at age three and six years.

When matched with the late and early insufficiency, early prenatal insufficiency of vitamin D with late sufficiency was linked with the declined occurrence of allergic rhinitis with aeroallergen sensitization at six years (aOR = 0.54) and three years (adjusted odds ratio [aOR] = 0.34)

As found, allergic rhinitis with sensitization considerably dropped at six years in offspring whose parents were given high-dose vitamin D (aOR = 0.54) than offspring whose parents were given low-dose vitamin D. Link of prenatal vitamin D with aeroallergen sensitization was enhanced in participants having a maternal atopy history and also who developed asthma.

Prenatal vitamin D sufficiency in the third trimester exhibits a protective effect on the occurrence of allergic rhinitis with aeroallergen sensitization in early childhood.