The California Department of Health Services is currently tracking the prevalence and demographic characteristics of autism. This data will be linked to hormone and protein markers measured during pregnancy. This is made possible though the California prenatal screening program, in which several hormones or protein markers were measured in maternal blood during the second trimester. In the proposed study, the levels of these hormone/protein in nearly 2,000 pregnant women and their offspring who are later diagnosed with autism, compared to the nearly 600,000 screened births during the same two years. Although hormonal factors have been frequently suggested as contributing to the occurrence or severity of autism, few studies have investigated this hypothesis. Significance: The results will help shape further research to rigorously evaluate complex interactions between genetic factors, in utero hormonal factors, and environmental factors in relation to autism. In addition to the analyses proposed, the investigators have numerous opportunities for follow-up, including examining similar parameters in other birth years, examining other newborn screening markers, and potentially obtaining newborn blood spots for genotyping. The proposed study provides a unique and cost-effective opportunity explore important data on a very large population.