According to a new study published in the Monday edition of the journal Pediatrics, the chances of autism in children who have an autistic older sibling are much higher than earlier perceived --- nearly one in five such children face a high risk of the disorder!

While previous smaller studies reported that the prevalence of autism in children with older autistic siblings was between 3 percent and 14 percent, researchers M. I. N. D. Institute in Sacramento have now found that the rates are actually much higher than that.

On the basis of an observation of 664 infants who had at least one older sibling suffering from autism, the new study found that as many as 19 percent ended up with an autism diagnosis before they had turned three.

Though the rates remained largely the same irrespective of the gender of the older sibling and the severity of that child's case, the researchers found that the 26 percent of the boys and 9 percent of the girls showed some form of autism.

In fact, experts also believe that having more than one older sibling with autism can further increase the chance of diagnosis to 32 percent --- with the calculations essentially being ‘average’, and the risk being either higher or lower for any given family.

Noting that the study is an important addition to autism research, Catherine Lord - director of the Institute for Brain Development at New York-Presbyterian/Weill Cornell Medical Center – said that the findings will have “critical implications for families who are deciding whether they'll have another child.”