In the study, researchers analyzed pediatricians' medical records on 64 children with autism; 34 boys with pervasive developmental disorder-not otherwise specified (considered an autism spectrum disorder); 13 boys with global development delay, 18 boys with other development problems and 55 typically developing kids.
Though they were of normal size at birth, compared to typically developing kids, boys with autism were longer at about 5 months old, had a larger head circumference at 9.5 months and weighed more by their first birthday.
The growth of the head was not out of proportion to the rest of the body; instead, the whole child grew bigger than normal, according to the study.
None of the children with other types of developmental problems showed similar growth patterns.
Boys who were in the top 10 percent for overall physical size in infancy had more severe social deficits and were lower functioning, according to the study.
Still, researchers stressed that "overgrowth" should not be used to diagnose autism, since not all kids who are later diagnosed with autism grow more rapidly than normal, and a large head circumference can indicate conditions other than autism.
However, pediatricians should play close attention to kids with an accelerated growth pattern, and perhaps refer them for genetic testing, Chawarska said.
Chawarska and her colleagues plan on conducting a similar study in girls, and investigating the possibility that interfering with overgrowth might help ease autism symptoms.
"That is highly speculative, and at this point we don't have a good model explaining how this might work," she noted.
Geraldine Dawson, chief science officer for Autism Speaks, an advocacy organization, said the study suggests interesting new areas of research, including t
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