They found that the placentas from ASD children were three times more likely to have the inclusions. Kliman and the team identified trophoblast inclusions by performing microscopic examinations of placental tissues.
"We knew that trophoblast inclusions were increased in cases of chromosome abnormalities and genetic diseases, but we had no idea whether they would be significantly increased in cases of ASD," said Kliman. "These results are consistent with studies by others who have shown that ASD has a clear genetic basis."
Trophoblast inclusions reflect abnormal folding of microscopic layers in the placenta and appear to result from altered cell growth. Kliman likened the presence of trophoblast inclusions to an automobile check-engine-light. "When the light goes on it simply means that something is not right," said Kliman. "If the light is on and there is, for example, steam coming from under the hood, then it is likely that the radiator is leaking. However, if the check engine light is on and there is nothing obviously wrong, then the car should be carefully checked."
The Yale team plans to replicate the evaluation with larger multi-center and prospective studies. They will examine the placentas of the children in the study in greater detail to gain insight into the biological basis of the inclusions in ASD.
Volkmar said, "If the work is confirmed by the next series of studies, then the finding of trophoblast inclusions at the time of birth in the absence of any obvious genetic abnormalities would be an indication to have a child examined by a specialist to determine the presence of ASD."