Prenatal and neonatal events were reported by parents of 13,690 eighteen-month-old twins enrolled in the Twins Early Development Study, a representative community sample born in England and Wales. At ages 7-8, parents and teachers completed questionnaires on social and nonsocial autistic-like features and parents completed the Childhood Asperger Syndrome Test. Correlations between prenatal and neonatal events and autistic-like features were weak, both in the whole sample (r = 0.00-0.07) and at the 5% quantitative extreme (phenotypic group correlations = 0.01-0.11), after controlling for socioeconomic status and cognitive ability. Neonatal problems showed modest heritability (13%-14%) and significant shared and nonshared environmental influences (55%-59% and 28%-31%, respectively). Differences in identical twins' neonatal problems correlated weakly with their difference scores on autistic-like features (r = 0.01-0.06). (Contains 5 tables.)