Children born to obese women are more likely to be diagnosed with autism or related developmental delays than the children of slimmer mothers, according to a US survey.
The research, which appeared in Pediatrics, was looking for the impact on childrens' cognitive development from a variety of"metabolic conditions" in the mother, including high blood pressure or diabetes.
The strongest links were found between obesity and autism-related disorders.
Although the study cannot prove that one condition causes the other, its authors caution that even the possibility is worrisome in the light of rising US obesity rates.
"If there is anything you can do to make yourself healthier, this is yet another reason for moms to consider," said Paula Krakowiak, a researcher at the University of California, Davis, who led the study.
The study comes on the heels of a report from the US Centers for Disease Control and Prevention that estimated one in every 88 children in the US has an autism spectrum disorder. That number represents about a 25 per cent increase from the agency's last report in 2006.
Krakowiak and her colleagues looked at 1,004 children who were between two and five years old, born in California and already participating in a study underway at UC Davis.
Of those children, 517 had an autism spectrum disorder and 172 had developmental delays. For Krakowiak's study, the children's diagnoses were confirmed by a re-evaluation at the UC Davis MIND Institute.
Milder versions of autism, such as Asperger's syndrome, form a "spectrum" of autism-related disorders. In addition, impairments in any one of the autism-related cognitive skill areas are considered developmental delays.
Among the children in the study with an autism spectrum disorder, 48 were born to mothers with Type 2 or gestational diabetes, 111 to mothers who were obese and 148 to mothers with any sort of metabolic condition, like high blood pressure.
For children with a developmental delay, 20 were born to mothers with Type 2 or gestational diabetes, 41 to mothers who were obese and 60 to a mother with any metabolic condition.
Overall, the connection between diabetes in a mother and her child being diagnosed with autism was not significant, but the researchers did find links between a mother being obese or having other metabolic conditions and her child having autism.
Developmental delays were associated with both obesity and diabetes, along with having any other metabolic condition.
"There is definitely an association present and it adds to the reasons for finding ways to lower obesity rates or diabetes rates and make greater efforts to change lifestyle factors,"Krakowiak said.
She and her colleagues also noted that nearly 60 per cent of US women of childbearing age are overweight, one third are obese and 16 per cent have so-called metabolic syndrome - a constellation of symptoms, including high blood pressure and insulin resistance, that raise heart risk.
Although nobody can say the nation's rising obesity rate is to blame for the prevalence of autism, Krakowiak said the parallel increases did catch her attention.
Hannah Gardener, an epidemiologist in the Department of Neurology at the University of Miami, told Reuters Health that she thinks it's natural for people to connect the two rates.
"There is a lot that is unknown and studies like these really help us figure out the questions that need to be answered," Gardener said.
But she warned that researchers are far from understanding what might create a link between obesity and autism.