A new study of more than 320,000 babies links autism to gestational diabetes.
The longitudinal study, conducted between 1995 and 2009 by researchers at Kaiser Permanente Southern California, found that children born to mothers who developed gestational diabetes before 26 weeks of pregnancy were at a 63 percent increased risk of being diagnosed with autism spectrum disorder. But after controlling for maternal age, education, ethnicity, household income, the child’s sex and the mother’s pre-existing conditions, that risk dropped to 42 percent.
While the overall rate of autism among study participants was 1 in 100 (mirroring national averages during the period of study), the rate of autism among children born to mothers with early pregnancy diabetes was 1 in 80.
Because this is a longitudinal association study, researchers were not able to establish a cause for the autism diagnosis. However, the associations were strong enough to warrant at least two health applications for expectant parents, according to study co-author Dr. Edward Curry.
For one, the study’s results emphasize the importance of early prenatal care. The women whose children were most at risk for developing autism were not women with previously diagnosed type 2 diabetes (who were already managing the condition with insulin, medication and diet). Nor were they women who got gestational diabetes after 26 weeks. Instead, the link between early gestational diabetes and an increased likelihood of autism diagnosis could mean that a fetus’ early exposure to uncontrolled high blood sugar may somehow affect brain development.
“We want to get mothers in early to make sure they’re on their vitamins, folic acid and that they check blood sugar to make sure it’s under control early on,” said Curry. “I think that’s the real takeaway message from this study."
The second application, according to Curry, is for moms who know they were diagnosed with gestational diabetes before 26 weeks. These moms should remain extra vigilant about their baby’s developmental milestones. Are they making eye contact, babbling and pointing? Parents should also tell their child's pediatrician about the gestational diabetes diagnosis, and ensure that pediatricians screen for autism appropriately at 12, 18 or 24 months old.
"We as pediatricians are supposed to be screening [by at least] 18 and 24 months, but it never hurts for the parents to have increased vigilance,” explained Curry. He also emphasized that his finding needs to be confirmed with more studies, as well as a few that can find out the causal link between gestational diabetes and autism, if there is one.
Dr. Annette Estes, the director of the University of Washington Autism Center, was not involved in Curry’s research but praised it for the large sample size, the length of time covered and the fact that the analysis controlled for multiple factors beyond gestational diabetes. The next step, said Estes, would be to do a prospective study, which looks forward in time by following pregnant moms, collecting data along their fetus’ growth and the child’s development. And, of course, the ultimate goal would be to figure out why there’s such a strong association between early gestational diabetes and the risk of autism diagnosis in children.
While scientists don’t know what exactly causes autism spectrum disorder, research to date suggests that a mix of genetic and environmental factors are at play. It’s known that autism tends to run in families and that having one child with autism increases the risk of subsequent siblings being diagnosed with the condition as well. Autism has also been linked in past studies to factors like air pollution, maternal obesity, periods of prenatal oxygen deprivation, exposure to pesticides and advanced parental age, according to the National Institutes of Health. The amount of preliminary research that’s out there right now can be confusing for parents and lay readers, explained Estes.
“The main factor that we are all in agreement is that genetics plays a major role in autism, but it doesn’t account for everything,” said Estes. "Once we get the genetics of autism a little more clear, then we can understand more about other risk factors; There’s going to be a number of risk factors, as we can see."
“I think at this point, what parents can take away is that [autism research] is a science that’s in process,” she concluded.
Autism is a lifelong disorder that is characterized by lack of eye contact, communication delays, difficulty forming relationships and a preoccupation with niche subjects or objects. Other behaviors typical in people with autism include rocking one’s body, banging one’s head against a hard surface and flapping one’s hands, although the severity of the condition can vary from person to person, ranging from mild impairment to severe disability.
Nationally, the Centers for Disease Control and Prevention has determined that currently, 1 in 68 children has been diagnosed with autism spectrum disorder, and that the condition is about five times more common in boys.
Curry's study was published online April 14 in JAMA.