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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 (= .00–.07) and at the 5% quantitative extreme (phenotypic group correlations = .01–.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 (= .01–.06).