FRIDAY, May 3 (HealthDay News) -- A much larger or much smaller
birth weight than average may be associated with an increased risk
of autism, according to a large new study.
Researchers examined data from more than 40,000 children in
Sweden, and found that those who weighed more than 9.9 pounds or
less than 5.5 pounds at birth were more likely to have autism than
those with a normal birth weight.
Specifically, smaller babies had a 63 percent greater risk, and
larger babies had a 60 percent greater risk. The link between birth
weight and autism risk was independent of whether or not a baby was
born premature or past the normal delivery date.
Autism is a neurodevelopmental disorder that affect a person's
ability to communicate and interact socially.
The study, published recently in the
American Journal of Psychiatry, is believed to be the first
to show a link between larger babies and increased autism risk and
confirms earlier research showing that low weight babies are more
likely to develop autism.
"We think that this increase in risk associated with extreme
abnormal growth of the fetus shows that something is going wrong
during development, possibly with the function of the placenta,"
study leader Kathryn Abel said in a university news release.
Abel is a professor at the Center for Women's Mental Health and
Institute of Brain, Behavior and Mental Health at the University of
Manchester, in England.
"Anything which encourages abnormalities of development and
growth is likely to also affect development of the baby's brain,"
she said. "Risk appeared particularly high in those babies where
they were growing poorly and continued in utero until after 40
weeks. This may be because these infants were exposed the longest
to unhealthy conditions within the mother's womb."
While the study found an association between having a high or
low birth weight and having autism, it did not establish a
"We now need more research into fetal growth, how it is
controlled by the placenta and how this affects how the brain
develops. One of the key areas to research is maternal condition
and healthy growth," Abel concluded.
The U.S. National Institute of Neurological Disorders and Stroke
has more about