April 9, 2012 at 8:49 AM ET
Women who are obese when pregnant may have a higher risk of having a baby with autism, a new study indicates.
Researchers found that the risk of autism increased by nearly 70 percent when moms were obese during their pregnancies, while the risk of a having a baby with some other neurodevelopmental disorder doubled, according to the study published early online Monday in Pediatrics.
Milder versions of autism, such as Asperger's syndrome and related conditions, form a "spectrum" of autism-related disorders. In addition, impairments in any one of the autism-related cognitive skill areas are considered developmental delays.
To take a closer look at the impact of obesity, diabetes and high blood pressure during pregnancy, the researchers compared medical histories of 315 typically developing children to those of 517 children with autism and 172 children with developmental disorders.
Moms with diabetes were slightly more likely to have a baby with autism, but the numbers weren’t large enough for the researchers to be sure that the association wasn’t just by chance. The association between a mom’s diabetes and some other neurodevelopmental disorder was stronger. In fact, diabetic moms were more than twice as likely to have a child later diagnosed with a neurodevelopmental disorder.
Researchers have been looking for preventable factors that contribute to the rise in the number of children with autism, said Dr. Andrew W. Zimmerman, director of clinical trials at the Lurie Center for Autism at the Massachusetts General Hospital for Children who is also on the faculty of the Johns Hopkins Bloomberg School of Public Health. “It’s very suggestive that this might be a real factor,” Zimmerman said.
That doesn’t mean that every obese woman is going to have a child with autism, he added. “But it’s one of the many things that goes into increasing the risk.”
Zimmerman would like to see more research on the topic. “Hopefully a larger one yet will be able to show what the effect of gestational diabetes is,” he said. “That’s a bigger question since a lot of women who don’t have any sign of diabetes develop gestational diabetes.”
It's unclear whether diabetes or obesity is actually impacting the growth of the fetus, but it’s always possible that these women have something else in common, said the study’s lead author Paula Krakowiak, a Ph. D. candidate at the University of California, Davis. But, said Krakowiak, “we’re seeing a rise in the rates of obesity and diabetes as well as a rise in autism.”
Krakowiak and her colleagues don’t yet know how obesity and diabetes might impact babies’ brain development, but they have some theories.
A possible culprit is the inflammatory proteins produced by the fat cells of an obese mom. “These same proteins are involved in the normal development of the brain,” Krakowiak said. “When the level of those immunological markers is higher or lower than the normal range it might affect how the brain develops in an adverse way. And at least one type has been shown to be able to cross over the placenta to the fetus.”
It’s also possible that the higher levels of blood glucose in obese and diabetic women could have a negative impact on the developing brain, since glucose can also cross over to the fetus, Krakowiak said. High levels of glucose could cause the baby to produce more insulin and also to grow faster, she added.
“When they’re growing at a faster rate, they require more oxygen and if the mom doesn’t provide enough oxygen then that could also cause some problems with brain development,” Krakowiak said.
Typically, a woman is considered obese when she's about 35 pounds overweight or more, or has a body-mass index of 25, experts say.
Krakowiak and her colleagues didn’t have information on inflammatory markers or insulin resistance in the moms in this study. That’s a subject for future research, she said.
Until researchers know more, obese moms might want to take the new findings as another reason to lose weight, Krakowiak said.
“That’s the safest message,” she added. “It doesn’t hurt anybody to lose weight and it comes with other benefits to the mom. So losing weight not only will help you, but it also might potentially help your child to be healthier.”
Reuters contributed to this report
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