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 this country.
Study women 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 Monday in Pediatrics.