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Background: Various studies have found reduced prevalences of atopic sensitization and atopic diseases in children previously exposed to infections or living conditions with a high microbial burden, such as the farming environment. Objective: We sought to determine the relationships of cord blood immunoglobulin E (IgE) with maternal health conditions before and during pregnancy. Methods: Pregnant women living in rural areas in five European countries were recruited in the third trimester of pregnancy. Information on maternal health during pregnancy was collected from maternity records and by questionnaires ( n = 497). Specific IgE for inhalant and food allergens was assessed in cord blood and peripheral blood samples of the mothers. Results: Inverse associations of cord blood IgE to seasonal allergens with positive maternal records for Toxoplasma gondii (adjusted odds ratio = 0.37 [0.17–0.81]) and rubella virus (adjusted odds ratio = 0.35 [0.13–0.96]) were found. The previously described effect of prenatal farm exposure on IgE to seasonal allergens was partly confounded by a positive maternal record for T. gondii. The number of maternal siblings, maternal contact to cats during pregnancy or during her first year of life, predicted a positive maternal record for T. gondii. Conclusions: Maternal immunity to T. gondii and rubella may impact on atopic sensitization in the fetus. A positive T. gondii record explained the previously identified effect of prenatal farm exposure on IgE to seasonal allergens only to a minor extent. [ABSTRACT FROM AUTHOR]