Birth Weight of Child Determines Risk of Autism, Researchers Say

The birth weight of a child can predict his or her risk of developing autism spectrum disorder (ASD), researchers say.

According to a team of researchers from The University of Manchester, babies who are either too small (weighing less than 2.5 kg) or too large at birth (more than 4.5 kg) are at greater risks of developing autism compared to babies having normal weight at birth.

Autism spectrum disorder (ASD) is a developmental disorder that leads to significant social, communication and behavioral changes. ASD starts normally by age 3 and stays throughout a person's life. Till now, there is no medical or blood test available for an early diagnosis of the condition. The behavior and development of a child are some factors used by health practitioners to determine the disorder.

A latest report from Centers for Disease Control and Prevention (CDC) states that one in every 50 school children in the U.S. is affected with autism. An early diagnosis can help in providing better treatment. Efforts have been going on for a long time to detect the warning signs and factors that lead to this condition.

To provide adequate evidence to prove the link between birth weight and autism, professor Kathryn Abel and colleagues went through nearly 40,000 child health records in Sweden between 2001 and 2007. It included details of about 589,114 children aged below 17 years.

Of the total number, 4,283 had autism and 36,588 were not affected by the disorder. At the end of the study, researchers noticed that a high birth weight increased the risk of autism by 60 percent, while low birth weight increased the risk by 63 percent.

Some of the changes that the uterus, particularly the placenta, undergoes during pregnancy may lead to this occurrence, researchers said.

"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," Abel said in a news release. "Anything which encourages abnormalities of development and growth is likely to also affect development of the baby's brain. 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."

The findings of the study have been published in The American Journal of Psychiatry.