Autism linked to obesity in pregnancy

Obese women are more likely to have children who develop autism than are normal-weight women, a new study suggests. The finding adds another possible explanation for the apparent rise in autism.

Reporting in the May Pediatrics, researchers also found that women who were obese or had some form of diabetes during pregnancy were more likely to have kids with developmental delays other than autism. And tests show that a woman’s obesity, diabetes or high blood pressure during pregnancy might have an effect on her offspring even if they don’t have autism, placing them at risk of slightly impaired learning.

The new research “sheds light on potential risk factors for autism and underscores the importance for people who are pregnant — or trying to get pregnant — of controlling their risks,” says epidemiologist Hannah Gardener of the University of Miami. “This is a very strong study.”

The authors note, however, that the findings show associations — not causes — of autism or developmental delays. “We can’t establish causation from this study,” says coauthor Irva Hertz-Picciotto, an epidemiologist at the University of California, Davis. “But it is interesting that obesity and diabetes are increasing as autism incidence is.” A recent study from the Centers for Disease Control and Prevention showed that 1 in 88 children born in the United States develops an autism spectrum disorder (SN Online: 4/3/12).

Previous studies have suggested that diabetes and hypertension in pregnancy might pose developmental risks to a fetus, but obesity has been studied less, Hertz-Picciotto says.

The researchers compared the pregnancy histories of mothers of 315 children who were developing normally, 172 children with developmental delays and 517 kids with an autism spectrum disorder — autism, Asperger’s syndrome and other social interaction problems. Symptoms of these disorders typically include repetitive or restrictive patterns of thoughts and behavior and struggles with language, communication, physical coordination, social skills and the sharing of emotions.

Obese mothers were 67 percent more likely to have an autistic child than normal-weight, healthy moms, the data show. Diabetes in pregnancy had no effect on autism risk, but mothers who were obese or who had some form of diabetes during gestation were about twice as likely to have a child with some form of developmental delay compared with healthier moms.

Many women who were obese, diabetic or hypertensive during pregnancy had children unaffected by autism spectrum disorders. On average, these children scored somewhat lower on tests of learning and adaptive behaviors than the kids without autism who had healthy, normal-weight moms.

The associations held even after researchers accounted for differences in race, education, time of year the kids were born, geographical region and mother’s age at delivery. 

The researchers could offer only speculation regarding a biological mechanism linking maternal obesity and autism risk, citing high blood sugar and high blood levels of insulin in the gestating mothers as a possible trigger for tissue damage in a fetus.

“We’ve got a long way to go in terms of figuring out environmental risk factors for autism … and how they interact with genetics,” Gardener says. The new study might spur lab and animal research aimed at finding the underlying cause of autism and other developmental disorders, she says.