The earliest indicator yet of autism may be the presence of flawed cells in the placenta, scientists have discovered. The findings could lead to earlier diagnosis of the developmental disorder that affects approximately one in every 200 children and can result in learning difficulties, speech problems and difficulty relating to people.

"The earlier we diagnose it, the more we'll understand the disease and the better and more potent our interventions may be," says research scientist Harvey Kliman of the Yale School of Medicine. Kliman and his team report their finding in the June 26 online issue of Biological Psychiatry.

The research builds on Kliman's previous work, which described abnormal, microscopic pits in the skin of the placenta. In the past, these abnormalities have been linked with a long list of genetic defects, including Down's syndrome and Turner's syndrome.

Kliman suspected that they may also be linked to autism. So in this study, he and other researchers at Yale used a microscope to examine tissue samples acquired from placenta saved by various research hospitals. Thirteen of the samples came from children later diagnosed with a form of autism; 61 samples came from children who were not diagnosed with the disease. When Kliman compared the two different kinds of tissue, he found that the placentas from the autistic children were three times more likely to have the abnormal microscopic pits.

Kliman thinks that the research could lead to routine analyses of placenta from at-risk newborns, particularly those with an older brother or sister with autism. Not every autistic child may be linked to the abnormal features on the placenta. But, says Kliman, "If you do see this feature, it's unlikely that the child is completely normal."