Prenatal exposure to household pets influences fetal immunoglobulin E production

Background Early life pet exposure may protect against allergic sensitization during childhood. Few studies have evaluated the effect of prenatal pet exposure on potential neonatal markers of allergic risk. Objective The aim of this study was to investigate whether maternal exposure to pets affects cord blood IgE levels in a population-based, general risk, ethnically mixed birth cohort. Methods Pet keeping during pregnancy was ascertained from women residing in a defined area of Wayne County Michigan and recruited from five staff model obstetric clinics. Maternal venous blood was analysed for total and allergen-specific IgE along with cord blood total IgE from 1049 infants. Results Compared with infants from households with no cats or dogs kept indoors during pregnancy, infants whose homes had either cats or dogs had significantly reduced mean cord IgE levels [0.34 IU/mL (95% CI 0.30-0.38) vs. 0.24 IU/mL (0.20-0.27), P=0.025]. Similar effects were apparent in cat-only households [0.21 IU/mL (0.16-0.27), P=0.020] and dog-only households [0.24 IU/mL (0.19-0.29), P=0.045]. There was no effect on results when excluding mothers who reported avoiding pets due to allergy-related concerns. Conclusion Mothers with either cats or dogs in their home during pregnancy deliver children with lower cord blood IgE levels compared with mothers who do not live with these pets, supporting the hypothesis that pet exposure influences immune development in a manner that is protective for atopy and is operant even before birth.