Large autism spectrum disorders (ASD) studies utilizing biobanks such as the National Children's Study are planned or underway but the financial cost of following children from birth is considerable and such studies will not yield reportable findings until years later. This is a case-control study of the early life environment that utilizes two existing resources with coverage of the entire nation of Sweden - a repository of 35+ years' worth of neonatal blood samples and the electronic health and population data registers. The question that is addressed is whether early life immune challenges (e.g., maternal infections and autoimmune disease) during pregnancy and the neonatal inflammatory response influence ASD risk. The approach is to conduct an epidemiological study in Sweden that links electronic health register data with laboratory data obtained from neonatal blood samples. For example, the Medical Birth Register contains data on the entire prenatal, perinatal, and early postnatal periods for all deliveries in Sweden. While these data have been used in previous Swedish investigations of ASD, they have never been linked with biosamples. The investigators will analyze inflammatory markers in blood samples collected for disease screening purposes (e.g., phenylketonuria or PKU) from all newborns born in Sweden since 1975 and stored at the National PKU Registry. The study utilizes a case-control design using all ASD cases born in Stockholm from 1998 to 2000 (N=648; high-functioning=313, low-functioning=335) and 1:1 age and sex-matched controls (N=648). For this sample, neonatal blood samples will be obtained and linked with register data on mother and child. The specific aims are to: 1) measure markers of inflammation in neonatal blood samples; 2) identify maternal immune and obstetric factors associated with inflammation in NDBS; 3) estimate the associations of inflammatory markers with future risk of ASD, while accommodating a wide range of covariates and confounders from both mother and child. Because inflammatory responses can be stimulated by numerous environmental exposures such as metals, stress, and air pollution, this study promises to provide valuable insight into a centralized mechanism by which varied genetic and environmental challenges may increase ASD risk. In summary, by linking electronic registers with biobank samples, this approach will provide a time-efficient and cost-effective means of fulfilling a 2011 Autism Speaks research priority regarding environmental risk factors.