A recent study has found that higher autism risk affects younger siblings, who are over a dozen times more likely than other children to have the disorder.
The risk of autism is not tied to a race or ethnicity, or whether children are born at term, early, or late. Gender appears to make a difference as well as birth order, according to the study published in the Journal of Developmental & Behavioral Pediatrics.
Researchers examined Kaiser Permanente medical records in Southern California, where at least two siblings were born to the same mother between 2001 and 2010. 592 our of 53,336 children were diagnosed with autism.
11.3 percent of children who had an older sibling on the spectrum were ultimately diagnosed with autism. Only 0.92 percent of other children had the developmental disorder. There was a higher risk for boys with older brothers who have autism, 15 percent compared to girls with older sisters on the spectrum who only were diagnosed 7 percent of the time.