April 2, 2008 -- Very premature birth may be a major risk factor for autism, but more study is needed
to confirm the association, researchers say.
One out of four very-low-birth-weight babies -- weighing as little as 1
pound at birth and no more than 3.3 pounds -- showed signs of autistic behavior
when screened as
toddlers in a study published in the April issue of the journal
The children, who are now preschool age, are undergoing further testing to
determine if they meet the diagnostic criteria for autism or related
"The very-low-birth-weight babies in our study did show a high
prevalence of autistic behaviors in early screening," study researcher
Catherine Limperopoulos, PhD, tells WebMD. "The next step is to determine
if what we are seeing in these early screenings really is autism."
Premature Birth and Autism
Ninety-one very-low-birth-weight children were included in the study,
conducted by researchers from McGill University and Harvard Medical School.
All were less than 3.3 pounds at birth, with gestational ages of 23 weeks to
In addition to routine developmental testing, the children were evaluated
signs of autism between the ages of 18 months and 24 months, using accepted
early screening tests.
Twenty-three of the 91 children (25%) had abnormal results on a screening
tool for behaviors associated with autism.
Boys were six times as likely as girls to have an abnormal score on the
screening test, and lower gestational age and weight at birth were also
associated with abnormal scores.
"The smallest and sickest babies seemed to be most at risk,"
The biggest single risk factor for a positive test was inflammation, usually
from a bacterial infection occurring before or during labor known as
The condition was associated with a 16-fold increase in
very-low-birth-weight babies testing positive for symptoms related to
Early Autism Screening Needed
Though the findings do not prove a link between very low birth weight and
autism, they do suggest a need for early screening in babies born weighing less
than 3.5 pounds, Limperopoulos says.
"We routinely screen these babies for language delays and motor
difficulties," she says. "Early autism screening should also be
She adds that it isn't yet clear if the behaviors associated with autism
identified through screening are lasting or transient.