Children born to mothers who are obese and have diabetes are more than 4 times as likely to be diagnosed with autism spectrum disorder compared with children born to mothers without diabetes who are a healthy weight, according to research published in Pediatrics.
While maternal diabetes has been associated with increased risk of autism in children, this is the first study to examine the combined effects of both obesity and diabetes on autism risk in children.
The researchers found that the combination of maternal obesity and diabetes was associated with a greater risk of autism in children than either obesity or diabetes alone. This provides evidence to a leading theory about autism: that the risk begins before the child is even born.
“We have long known that obesity and diabetes aren’t good for mothers’ own health,” said Xiaobin Wang, MD, ScD, MPH, the Zanvyl Krieger Professor in Child Health at the Bloomberg School and director of the Center on the Early Life Origins of Disease in a statement. “Now we have further evidence that these conditions also impact the long-term neural development of their children.”
The researchers analyzed 2734 mother-child pairs, a subset of the Boston Birth Cohort recruited at the Boston Medical Center between 1998 and 2014. They collected data on mothers’ pre-pregnancy weights and noted whether mothers had diabetes before getting pregnant or whether they developed gestational diabetes.
The researchers followed the children from birth through postnatal study visits and a review of electronic medical records, identifying 102 children who were diagnosed with autism during the course of the study (with a median length of postnatal follow-up of 6 years). They found that children whose mothers were both obese and diabetic were more than 4 times as likely to be diagnosed with autism compared with children whose mothers were of a normal weight and without diabetes.
Along with children of mothers who had diabetes before pregnancy, children of obese mothers who developed gestational diabetes during pregnancy were also at a significantly increased risk of developing autism.
“It’s important for us to now try to figure out what is it about the combination of obesity and diabetes that is potentially contributing to sub-optimal fetal health,” said M. Daniele Fallin, PhD, chair of the Bloomberg School’s Department of Mental Health and director of the Wendy Klag Center for Autism and Developmental Disabilities in a statement.
The biology behind why obesity and diabetes contribute to autism risk is not well understood. Previous research has shown that obesity increases circulating proinflammatory cytokines in pregnant women, which may lead to brain inflammation in the fetus. Other studies suggest that obese women have less folate, a B-vitamin vital for human development and health.
In diabetic mothers, hyperglycemia “triggers fetal hyperinsulinemia and increased oxygen consumption, inducing chronic intrauterine fetal tissue hypoxia,” the authors wrote. “Maternal hyperglycemia is also associated with an increased production of free radicals and oxidative stress.” Both hypoxia and oxidative stress have been associated with autism development.
For these reasons, co-occurring obesity and diabetes may act as “multiple hits” to the developing fetal brain, creating an even greater risk of autism than obesity or diabetes alone.
The researchers note that women of reproductive age who are considering having children need to not only consider the effects of obesity and diabetes on their own health, but consider the effects it could have on their children.
Li M, Fallin MD, Riley A, et al. The Association of Maternal Obesity and Diabetes With Autism and Other Developmental Disabilities. Pediatrics. 2016; doi:10.1542/peds.2015-2206.