While studies report associations between perinatal outcomes and both autism spectrum disorder (ASD) and intellectual disability (ID), there has been little study of ASD with versus without co-occurring ID. We compared perinatal risk factors among 7547 children in the 2006–2010 Autism and Developmental Disability Monitoring Network classified as having ASD + ID, ASD only, and ID only. Children in all three groups had higher rates of preterm birth (PTB), low birth weight, small-for-gestational-age, and low Apgar score than expected based on the US birth cohort adjusted for key socio-demographic factors. Associations with most factors, especially PTB, were stronger for children with ID only than children with ASD + ID or ASD only. Associations were similar for children with ASD + ID and ASD only.
