Researchers at the Yale School of Medicine have figured out how to measure an infant's risk of developing autism at birth - by looking for abnormalities in the placenta. In the future this may allow earlier diagnosis and treatment of this developmental disorder.

One out of 50 children in the US are diagnosed with autism every year, but the diagnosis is usually made when these children are 3-4 years of age or older. Unfortunately by then the best opportunities for intervention have already been lost because the brain is typically the most responsive to treatment in the first year of life.

The authors of this groundbreaking new study have found abnormal placental folds and abnormal cell growths called trophoblast inclusions that help to identify newborns at high risk for autism.

The research team examined 117 placentas from infants of at-risk families - those with one or more previous children with autism. These at-risk placentas were then compared to 100 control placentas collected from the same geographic area.

They found that the at-risk placentas had as many as 15 trophoblast inclusions, while none of the control placentas had more than two trophoblast inclusions. A placenta with four or more trophoblast inclusions means an infant with a 96.7% probability of risk for autism.

Currently, the best early marker of autism risk is family history. Couples with an autistic child are nine times more likely to have another child with autism.

In the past couples without known genetic susceptibility had to rely on identification of early signs that may not manifest until the child's second or third year of life. But now thanks to this new finding, at-risk families can employ early intervention strategies to improve outcomes.

The study authors hope that diagnosing risk of developing autism by examining the placenta at birth will become routine, so that the children with increased numbers of trophoblast inclusions can have earlier, successful interventions and an improved quality of life.