Prenatal exposure to a farm environment modifies atopic sensitization at birth.

Pregnant women living in rural areas in Austria, Finland, France, Germany, and Switzerland were recruited in the third trimester of pregnancy. Information on maternal farm-related exposures, nutrition, and health during pregnancy was obtained by means of interviews. Specific IgE levels for food and common inhalant allergens were assessed in cord blood of 922 children and peripheral blood samples of their mothers. Different sensitisation patterns in cord blood of farm and nonfarm children were observed. In multivariable analysis consumption of boiled, but not unboiled, farm milk during pregnancy was positively associated with specific IgE to cow's milk independently from maternal IgE. In contrast, there was an inverse relationship between maternal exposure to animal sheds and cord blood IgE levels against seasonal allergens (adjusted odds ratio, 0.38; 95% CI, 0.21-0.70). This association was not confounded by maternal IgE levels. Maternal contact with hay enhanced the protective effect of exposure to animal sheds on IgE levels to grass pollen in cord blood. The results suggest that maternal exposure during pregnancy influences atopic sensitisation patterns in cord blood. The (microbial) context of allergen contact possibly modifies the risk of atopic sensitisation. J Allergy Clin Immunol. 2008;122(2):407-12, 412.