Among environmental factors that may confer risk for autism, perinatal factors are prominent. Based on multiple lines of research, it has been hypothesized that activity of the hormone oxytocin – a 'social' hormone that mediates affiliative behaviors in many species including humans – may be a perinatal factor that impacts the risk of autism spectrum disorders (ASD). This study will take an epidemiological approach to determining the roles of Pitocin and Atosiban in ASD. Dr. Ebstein and colleagues will recruit mother and child pairs from four categories: mothers having received Atosiban during pregnancy; mothers having received Nifedipine, a drug used to prevent preterm labor that does not affect oxytocin signaling; mothers that received Pitocin during labor; and a matched control group of mothers who received no drugs and delivered at term. Children of these mothers will be screened for neurodevelopmental delays, and those testing positive will undergo further evaluations for ASD.