"We can look at the placenta at birth and determine the chance of being at risk for autism with extremely high reliability," said Dr. Harvey Kliman, a research scientist at Yale University. One of 88 U.S. children has an autism spectrum disorder, the umbrella name for complex brain development disorders marked by problems with social interaction and communication, according to the U.S. Centers for Disease Control and Prevention.
The earlier autism is treated, the better the outcome. But children typically aren‘t diagnosed until behavioral symptoms begin, perhaps at age 2 or 3 years, or even later. Kliman said the children identified as at risk at birth might benefit from early treatment.
For the new study, published online April 25 in the journal Biological Psychiatry, Kliman and his team examined 117 placentas from newborns whose mothers already had one or more children with some form of autism, which put the infant at higher risk for the disorder. The researchers compared those samples with placenta samples from 100 women who already had one or more typically developing children.
During pregnancy, the placenta keeps the unborn baby‘s blood supply separate from the mother‘s while providing the baby with oxygen and nutrients. At delivery, the placenta, also called the afterbirth, follows the baby out of the womb.
The placentas from women whose older children had autism were markedly different from the others, Kliman‘s team found. They zeroed in on abnormal folds and abnormal cell growth in the placenta, known as trophoblast inclusions.
The placentas from the at-risk pregnancies were eight times more likely to have two or more of these abnormal folds than samples from not-at-risk deliveries. Placentas with four or more of the inclusions predicted an infant with at least a 74 percent probability of being at risk for autism, the researchers said.
"There were no [placentas from pregnancies not at risk] that had more than two of the folds," Kliman said.
The study only predicted risk of autism, however, not actual autism. The researchers will continue to follow the children.
The testing can‘t be done before delivery, Kliman said. "You need enough placenta [to examine]."
But the test could help spot at-risk children much earlier than is now possible, Kliman suggested. "There is no way [currently] to know at birth that your child might have autism," he said. "If you know you have a child who is at risk for autism at birth, you are ahead of the game." Interventions can begin early, when the brain is more open to change.
How the folds in the placenta relate to autism risk isn‘t clear, Kliman said. He and others speculated that the abnormalities in the placentas and the brains of the children affected with autism are marked by increased cellular growth, which then leads to the unusual folding. "The heads of children with autism are bigger," he said. Their brains grow rapidly early in life.
"I‘d like to see it as a routine test," Kliman said. The test is labor intensive and requires pathology, however, and Kliman estimated it could cost $2,000 or more.
This isn‘t the first study to link placental abnormalities with autism risk, said Geraldine Dawson, chief science officer for Autism Speaks, an advocacy and research group. "However, it is one of the largest studies to confirm this finding," she said.
But more research is needed to confirm the findings, she said.
It is too soon to suggest this as a routine test, said Dr. Daniel Coury, medical director of the group‘s Autism Treatment Network and chief of developmental and behavioral pediatrics at Nationwide Children‘s Hospital in Columbus, Ohio. He praised the study, but also said more research is needed to duplicate the findings.
"Being able to identify those infants at greater risk so we can target our interventions is really big news," he said.
The study was supported by the National Institutes of Health; the MIND Institute at the University of California, Davis; Yale University Reproductive and Placental Research Unit; and the U.S. Environmental Protection Agency. The researchers don‘t hold patents on the procedure or have financial interests in it.
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