Pregnancy and birth complications in autism and liability to the broader autism phenotype

Objective: To understand better the relationship between pregnancy and birth complications and genetic factors in autism. Method: The sample included 78 children with an autism spectrum disorder and 88 unaffected siblings. A standardized interview was used to ask mothers about the pregnancy and birth of each child, and an overall index reflecting freedom from complications (termed "optimality") was determined. The presence of autism-like traits (termed the "broader autism phenotype") in second- and third-degree relatives was ascertained by reports from multiple informants. The proportion of relatives with the broader autism phenotype, corrected for degree of relation, was used as an index of family loading. Results: Children with autism spectrum disorders have lower optimality (higher rates of complications) than unaffected siblings. High family loading for the broader autism phenotype is associated with higher rates of complications in unaffected siblings. Family loading was not significantly associated with complications in affected siblings in this sample. Overall, these findings argue against complications being a direct cause of autism, as one would expect to find the most complications in sporadic cases (i.e., in children without a positive family history). Conclusion: Increased rates of birth and pregnancy complications are likely secondary to familial factors associated with autism.