Established in 1989, the Nurses Health Study II has prospectively evaluated many aspects of women's health in a cohort of over 100,000 women in the United States. The information collected on this group include medical, obstetrical, and prospectively collected dietary factors, as well as neurodevelopmental diagnosis of children born to women in this cohort. This allows for a unique opportunity to investigate a wide range of environmental factors, including maternal dietary and reproductive factors, which may be associated with risk of developing autism spectrum disorders. Diet and medical history of mothers with a child with autism, as well as those who did not report a child diagnosed with autism, will be studied using information gathered prior to pregnancy. These children and their parents will be screened using the social responsiveness scale (SRS) and then followed up by the Autism Diagnostic Instrument-Revised (ADI-R). Utility of the SRS, which measures autism severity using one quantifiable score, as a diagnostic instrument will also be investigated in this study.