Intrauterine life and infancy are critically sensitive periods in brain development. The role of preventable prenatal and neonatal factors on the risk of psychiatric and neurodevelopmental disorders is unclear. Maternal characteristics influence risks of pregnancy, delivery, and neonatal complications which may in turn affect neurodevelopmental processes. Nevertheless, a mechanistic sequence connecting these events has not been described. Using linkage of nation-wide registries, we propose to conduct a population-based cohort study of 3.4 million singleton children born 1983-2016 in Sweden, to examine the associations of maternal factors as well as pregnancy, delivery, and neonatal complications with the risks of psychiatric and neurodevelopmental disorders (depressive disorder, bipolar disorder, suicide, schizophrenia, anorexia nervosa, autism, intellectual disability, epilepsy, and cerebral palsy). We will pursue complementary analytic approaches to strengthen causal inference including studies of exposure change between pregnancies, matched sibling case-control studies, full mother-sibling pairs case-control studies, and mediation analyses. The Swedish nation-wide registries constitute the largest and most complete data source worldwide to address these questions.