Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Autism Spectrum Disorders Health Center

Font Size

Extreme Birth Weights Tied to Autism

Newborns who weigh much more or less than average may be at risk for disorder, researchers say

WebMD News from HealthDay

By Robert Preidt

HealthDay Reporter

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 cause-and-effect relationship.

"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.

Today on WebMD

girl at window
Symptoms within the first 2 years of a child’s life.
boy playing a violin
How is this condition similar to autism?
Mother and daughter indoors playing
Play therapy may undo the disorder in at-risk babies.
preschool age girl sitting at desk
What causes this rare form of autism?
High Functioning Autism And Asperge Syndrome
Gluten Free Diet Slideshow
Mother and daughter indoors playing
man on bicycle
girl at window
Mother hugging teenage son
Understanding Rett Syndrome
Home Care Tips

WebMD Special Sections