Background: The immunological environment during pregnancy may differ between allergic and non-allergic women. This study investigates the effect of maternal allergy on the allergen-induced cytokine and chemokine levels and whether pregnancy modulates these immune responses differently in allergic and non-allergic women. Methods: The birch-, cat-, phytohemagglutinin- and tetanus toxoid-induced interferon-gamma(IFN-gamma), interleukin (IL)-4, IL-5, IL-10, IL-13, the T-helper 1 (Th1)-associated chemokine CXCL10 and the Th2-associated chemokine CCL17 levels were quantified in 20 women with allergic symptoms (sensitized, n=13) and 36 women without allergic symptoms (non-sensitized, n=30) at gestational weeks 10-12, 15-16, 25, 35 and 2 and 12months post-partum. Results: Birch-, but not cat-induced, IL-5, IL-13 and CCL17 levels were increased during pregnancy as compared to post-partum in the sensitized women with allergic symptoms. In contrast, cat-, but not birch-induced, IL-5 and IL-13 levels were increased during pregnancy as compared to post-partum in the non-sensitized women without allergic symptoms. Furthermore, IFN-gamma secretion was increased in the first and decreased in the second and third trimesters in response to birch and decreased in the third trimester in response to cat as compared to post-partum in the non-sensitized women without allergic symptoms. Increased allergen-induced IL-4, IL-5 and IL-13 levels were associated with allergic symptoms and sensitization. Conclusions: Pregnancy had a clear effect on the allergen-induced IL-5, IL-13, CCL17, IFN-gamma and CXCL10 production, with distinct enhanced Th2-responses to birch in the allergic group and to cat in the non-allergic group.