The research, which was looking for effects on kids' cognitive development from a variety of "metabolic conditions" in mom -- including high blood pressure or diabetes -- found the strongest links between obesity and autism-related disorders.
Researchers also found ties between the other maternal metabolic conditions and developmental delays in kids.
Although the study cannot prove that one condition causes the other, its authors, who published their results in the journal Pediatrics, caution that even the possibility is worrisome in light of rising U.S. 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.
Krakowiak and her colleagues looked at 1004 children who were between two and five years old, born in California and already participating in a study underway at UC Davis.
Of those kids, 517 had an autism spectrum disorder and 172 had developmental delays. For Krakowiak's study, the children's diagnoses were confirmed by a reevaluation at the UC Davis MIND Institute.
Autism is attributed to atypical brain development and characterized by a group of symptoms that include problems with socialization, communication and behavior.
Milder versions of autism, such as Asperger's syndrome and related conditions, 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 kids 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 moms 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 moms with any sort of 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 any other metabolic condition 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," said Krakowiak.