Placental trophoblast inclusions in autism spectrum disorder

Background: Microscopic examination of placental tissue may provide a route to assessing risk and understanding underlying biology of autism. Methods: Occurrence of a distinctive in microscopic placental morphological abnormality, the tropboblast inclusion, was assessed using archived placental tissue. The rate of occurrence of trophoblast inclusion-positive slides observed for 13 individuals with autism spectrum disorder (ASD) was compared to the rate in an anonymous consecutive birth cohort. Results: The occurrence of inclusion positive slides was significantly greater in the ASD group compared to the control group (6127 slides, 22.2% vs. 12/154, 7.8%; Fisher Exact Test, two-tailed p = .033; relative risk 2.85). The proportion of positive cases was also greater in the ASD group (5/13 cases, 38.5% vs. 8/61, 13.1%; Fisher Exact, two-tailed p = .044; relative risk 2.93). Behavioral severity scores did not differ across groups of inclusion positive (N = 4) and negative (N = 8) ASD individuals. Conclusions: Although probably not functionally detrimental or causative, the greater occurrence of placental trophoblast inclusions may reflect altered early developmental processes. Further research is required to replicate the basic finding, to understand the basis for the trophoblastic abnormality, and to determine the utility of the measure in early detection of ASD.