The Autism Birth Cohort (ABC): a study of autism spectrum disorders in MoBa.

Background: Autism spectrum disorders ( ASDs) are characterized by persistent deficits in social communication and interaction and restricted, repetitive patterns of behavior, interests or activities. In most cases, the cause of ASDis likely to be a combination of genetic predisposition and environmental exposures occurring in fetal life or early infancy. Consequently, a prospective pregnancy cohort like MoBa represents an ideal platform for studies of ASDsin children. Methods: The Autism Birth Cohort (ABC) Study has identified potential ASDcases in MoBa through questionnaire- based screening, parental and professional referrals, and linkages to the Norwegian Patient Register. ASDdiagnoses have been ascertained through in-person clinical assessments and medical record reviews. Current results : By the end of 2012, the ABC Study had identified 518 ASDcases in MoBa. The ASDprevalence in school-age children is 0.7-0.8%, which is in line with nationwide estimates for Norway. The most important source of ASDcase identification was registry linkages, while only a minority was detected through early screening. Published findings show that screening at 18 months misses the majority of ASDcases. Analyses of risk factors for ASDshave shown that maternal use of folic acid supplementsin early pregnancy may lower the child’s risk of developing ASDsand that paternal obesity appears to increase the child’s risk of ASDs. Future plans: ASDcase identification will continue through annual registry linkages and subsequent reviews of medical records. Analyses of plasma samples and RNA samples will be conducted to investigate prenatal and perinatal microbial exposures, innate immune and inflammatory responses, biomarkers of autism risk, and exposures to xenobiotics. Analyses of deciduous teethwill also investigate the effect of medications and environmental toxins. Exome sequencing of DNA from ASDcases and their parents is ongoing, and will elucidate the role of de novo DNA mutations in the pathogenesis of ASDs. Future epidemiological analyses will explore the results of the 36-month screening for ASDs, the diagnostic stability and developmental trajectories in ASDchildren, and psychiatric and medical comorbidities in ASDs.