(CNN) - Although researchers know that children with older siblings who have autism spectrum disorder, or ASD, have a higher risk of developing the condition themselves, a new study in the journal Pediatrics finds that risk is even higher than previously expected.
Researchers monitored more than 600 infants who either had an older biological brother or sister with ASD. They followed the little ones from infancy to 36 months.
Previous studies estimated the ASD recurrence risk in younger siblings was between 3 and 10 percent. But this study found that the overall risk was much higher, at 18.7 percent, and even higher in families with more than one affected sibling, about 32 percent.
As for the sex of the children, male babies experienced nearly three times the risk over female infants, 26 versus 9 percent.
Age of parent, gender of the older sibling or birth orders were not predictors of the condition.
Authors of the study suggest their findings could impact future genetic screening and family planning decisions when it comes to parents whose first born has ASD.
The knowledge could lead to earlier observation and intervention for those young siblings.
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