Objectives. We assessed the association between assisted reproductive technology (ART) and diagnosed autistic disorder in a population-based sample of California births. Methods. We performed an observational cohort study using linked records from the California Birth Master Files for 1997 through 2007, the California Department of Developmental Services autism caseload for 1997 through 2011, and the Centers for Disease Control and Prevention’s National ART Surveillance System for live births in 1997 through 2007. Participants were all 5 926 251 live births, including 48 865 ART-originated infants and 32 922 cases of autism diagnosed by the Department of Developmental Services. We compared births originated using ART with births originated without ART for incidence of autism.Results. In the full population, the incidence of diagnosed autism was twice as high for ART as non-ART births. The association was diminished by excluding mothers unlikely to use ART; adjustment for demographic and adverse prenatal and perinatal outcomes reduced the association substantially, although statistical significance persisted for mothers aged 20 to 34 years. Conclusions. The association between ART and autism is primarily explained by adverse prenatal and perinatal outcomes and multiple births
