The study of more than 1,000 children in California found the risk of autism and other developmental delays was 60 percent higher among those born to mothers who were obese, hypertensive or diabetic.
"The prevalence of obesity and diabetes among U.S. women of childbearing age is 34 percent and 8.7 percent, respectively," the study authors wrote in their report published today in the journal Pediatrics. "Our findings raise concerns that these maternal conditions may be associated with neurodevelopmental problems in children and therefore could have serious public health implications."
The U.S. Centers for Disease Control and Prevention in Atlanta estimates one in 88 children has an autism spectrum disorder, up from one in 110 in 2006. Obesity is also on the rise, affecting more than one-third of U.S. adults.
"It's hard to say if they're linked," said study author Irva Hertz-Picciotto, professor of public health sciences at the University of California at Davis. "It might be there's some environmental factor that contributes both to the obesity epidemic and to the rise in autism cases. Or it could be the increase in obesity is, in fact, contributing to the increase in autism. But it's certainly not going to account for all of it."
"The goal of our research program is to try to find the modifiable risk factors," Hertz-Picciotto said. "You can't control your genetics. … But assuming our study is replicated, you would really want to figure out whether lowering weight and controlling diabetes during pregnancy through physical exercise and diet or more medical means could change the risk of a child developing autism."
How obesity and diabetes during pregnancy might predispose the developing fetus autism is unclear, but theories include overexposure to glucose, insulin and inflammation.
"This study doesn't tell you anything about the origin of autism. What it does tell you are things associated with autism," said Dr. Susan Hyman, associate professor of pediatrics at the University of Rochester Medical Center. "We would not advocate treating the hypothetical causes of autism, but we would recommend women of childbearing years to eat healthy and exercise and take care of themselves, not only for the fetus but so they can see their children grow up."
While maternal obesity is linked to a modest increase in autism risk, Hyman said it can have other health consequences in mother and child. Previous studies have linked maternal obesity to birth defects, including spina bifida as well as heart and limb deformities.
"Obesity is a major public health problem," she said. "The risk for autism and developmental disorders is only part of it."
Hyman said autism is a complex condition thought to emerge from an interaction of multiple genetic and environmental influences.
"Any time a child is diagnosed with autism, the parents pour over everything that they were exposed to: what they ate; what they drank; when they were ill. But each of these contributors is very small," she said, stressing that mothers should not feel guilty if they were obese during pregnancy.
Dr. Ari Brown, an Austin, Texas-based pediatrician and author of "Baby 411," said the study is one more piece in the puzzle of autism spectrum disorders, a collection of conditions with varying symptoms and, quite likely, multiples causes.
"I think we're just beginning to unravel some of the mysteries of autism spectrum disorders. And I don't think we're going to find just one answer because it's not just one disease," Brown said. "But it's really important for women prior to do a preconception visit with their doctor and talk about attaining ideal body weight prior to becoming pregnant. Being overweight or obese can lead to a variety of health problems for mom and baby."