CHICAGO – Obesity during pregnancy may increase chances for having a child with autism, provocative new research suggests.
It’s among the first studies linking the two, and though it doesn’t prove obesity causes autism, the authors say their results raise public-health concerns because of the high level of obesity in the U.S..
Women in the study who were obese during pregnancy were about 67 percent more likely than normal-weight women to have autistic children. They also faced double the risk of having children with other developmental delays.
On average, women face a 1 in 88 chance of having a child with autism; the results suggest that obesity during pregnancy would increase that to a 1 in 53 chance, the authors said.
The study was released online in Pediatrics.
The study is a good start, but further work should be done, says Dr. Richard Grossman, who practices gynecology in Durango and is a columnist for The Durango Herald.
“I tend to think the study is pretty valid. It was peer reviewed, but I have some concerns,” Grossman said Thursday.
There were 1,004 children in the study, but that’s a fairly small number for such an important issue, he said. “A study has to have a huge number of people if it’s going to tease out significance with many confounding factors.”
Obesity is bad, whether a person is young or old, but it’s especially bad for pregnant women, Grossman said.
“Obesity affects pregnancy in ways still not understood,” Grossman said. “We don’t understand why the stillbirth rate in obese women is double that of women of normal weight, even if all other factors are controlled.”
In the Pedriatrics article, Grossman said, there was not adequate control for socioeconomic factors such as income level, tobacco, alcohol or drugs, Grossman said.
There also is a faddish aspect to the autism-obesity link, Grossman said.
“At one time in the recent past, we gave a lot of attention to the manic-depressive spectrum,” Grossman said. “It’s still around but not like a decade ago. Who knows what psychological diagnosis will be next?”
Grossman said a prospective study of the obesity/autism syndrome – following methodically over time the relationship between a condition shared by members of a group – is needed.
This wasn’t done in the study in question, he said.
“They relied on the memory of the mother in which ‘recall bias’ can occur,” Grossman said. “A mother with an autistic child is more likely to blame it on obesity because she is looking for a cause.
“The correlation between obesity and autism is probably real,” Grossman said. “The study in question is a good starting point for a more controlled study.”
Researcher Paula Krakowiak, a study co-author and scientist at the University of California, Davis, said that because more than one-third of U.S. women of child-bearing age are obese, the results are potentially worrisome and add yet another incentive for maintaining a healthy weight.
Previous research has linked obesity during pregnancy with stillbirths, preterm births and some birth defects.
Dr. Daniel Coury, chief of developmental and behavioral pediatrics at Nationwide Children’s Hospital in Columbus, Ohio, said the results “raise quite a concern.”
He said that U.S. autism rates have increased along with obesity rates, and said the research suggests that may be more than a coincidence.
More research is needed to confirm the results. But if mothers’ obesity is truly related to autism, it would be only one of many contributing factors, said Coury, who was not involved in the study.
Genetics has been linked to autism, and scientists are examining whether mothers’ illnesses and use of certain medicines during pregnancy might also play a role.
The study involved about 1,000 California children, ages 2 to 5. Nearly 700 had autism or other developmental delays, and 315 did not have those problems.
Mothers were asked about their health. Medical records were available for more than half the women and confirmed their conditions. It’s not clear how mothers’ obesity might affect fetal development, but the authors offer some theories.
Obesity, generally about 35 pounds overweight, is linked with inflammation and sometimes elevated levels of blood sugar. Excess blood sugar and inflammation-related substances in a mother’s blood may reach the fetus and damage the developing brain, Krakowiak said.
The study lacks information on blood tests during pregnancy. There’s also no information about women’s diets and other habits during pregnancy that might have influenced fetal development.
There were no racial, ethnic, education or health-insurance differences among mothers of autistic kids and those with unaffected children that might have influenced the results, the researchers said.
The National Institutes of Health helped pay for the study.