The causes of Autism Spectrum Disorders (ASDs) are not known, but there is evidence to suggest that environmental exposures may influence ASD risk. Immune activity in mothers during pregnancy has been suggested to be related to risk of ASD, and some occupational and environmental exposures can trigger an immune response. However, such exposures during pregnancy have not yet been studied in autism. The overall goal of this project is to examine the impact of occupational exposures to asthmagens (agents that can cause asthma) during pregnancy on ASD risk. Previous studies of environmental risk factors for ASDs have been limited by lack of data on exposures and lack of confirmation of ASD diagnoses. To overcome this, two comprehensive epidemiology studies will be used that have occupation information during pregnancy on mothers and fathers and also have in-depth diagnostic information, in addition to a large amount of other data on lifestyle, medical history, and genetics of parents and children: the Study to Explore Early Development (SEED), a national study of autism and the Early Autism Risk Longitudinal Investigation (EARLI) study, a pregnancy study that follows mothers through birth and children through the first 3 years of life. In aim 1, the association between parental exposures to occupational asthmagens and ASDs will be examined in the SEED study. In aim 2, the association between parental exposures to occupational asthmagens and behaviors at 6 and 12 months of age will be evaluated in the EARLI study. In aim 3, possible maternal genetic predisposition to these exposures will be considered. In aim 4, the association between a biological marker of immune response in mothers during pregnancy (prenatal serum IgE levels) and infant behaviors will be examined in EARLI. This final aim will serve as complementary evidence to support any detected occupational associations. This work will lead to a better understanding of the environmental conditions and immune responses that may influence risk of ASDs. Learning more about the causes of ASDs may lead to earlier detection, improved care, and possibly prevention.