The risk was especially pronounced among low birth-weight girls, said the authors of the study, which was published in the June issue of Pediatrics. Baby girls weighing less than 2.5 kilograms, or about 5.5 pounds, had 3.5 times increased risk of autism. Baby girls born more than seven weeks early had a 5.4 times increased risk.
Babies born with low birth weights are likelier to have bleeding in the brain, lungs that are more likely to collapse, heart problems and vision loss.
Boys born with low birth weight or prematurely didn't have a significant difference in their risk of being autistic, the report said. The study, which was carried out by researchers at the U.S. Centers for Disease Control and Prevention, studied children born from 1981 to 1993 in Atlanta.
More than 550 children with autism were paired to normal children born in the same year.
There was also double the risk for developing autism in babies born prematurely, although this was primarily due to a more than fivefold increased risk in girls born early.
Autism is a brain development disorder that impairs social interaction and communication, and causes restricted and repetitive behavior, all starting before a child is three years old. The child may refuse to engage with other people, echo words and phrases, or repeat actions many times.
Autism and related disorders, some of them less severe, affect about 1 in 150 U.S. children. There is no cure for the disorder but proper guidance and prognosis can hugely effect the behavior.
According to the National Institute for Neurological Disorders and Stroke, some three to six children out of every 1,000 will have autism, while males are four times more likely to develop the disorder than girls.
