In the United States, approximately 64% of women of childbearing age are either overweight or obese. Maternal obesity during pregnancy is associated with a greater risk for adverse maternal-fetal outcomes. Adverse health outcomes for the offspring can persist into adulthood, increasing the incidence of several chronic conditions including cardiovascular disease, diabetes, and asthma. Since these diseases have a significant inflammatory component, these observations are indicative of perturbation of the normal development and maturation of the immune system of the offspring in utero. This hypothesis is strongly supported by data from several rodent studies. In this thesis we examine the impact of maternal obesity on the neonatal immune system.