In the largest study of its kind, researchers say they’ve found a higher risk of autism among children whose births were induced or sped up.

The finding comes from a study published Monday in the journal JAMA Pediatrics looking at 625,042 births in North Carolina over eight years. Researchers at Duke University and the University of Michigan compared the children’s birth records with public school records to assess whether or not the kids were later diagnosed with autism.

The percentage of mothers who were induced or had their labor sped up was higher among children with autism, the study found.

In the most extreme example, boys born after labor was both induced and accelerated had a 35 percent higher chance of autism as compared to children born without the aid of either treatment. Meanwhile, researchers found that in cases where either inducing or speeding up labor — but not both — was involved there was a higher risk of autism in boys, but only accelerating labor increased the odds for girls.

It’s unclear precisely what’s behind the link, researchers said. There could be underlying problems with the pregnancies that lead to the need for doctors to intervene or it could be something about the process of inducing or speeding up labor or the drugs used to do so, they said.

“This study provides preliminary evidence of an association between autism and labor induction/augmentation, especially among male children,” said Marie Lynn Miranda of the University of Michigan and a senior author of the study.

The increased chance for autism observed in the study is similar to that of other known risk factors like a mother being older or a baby being born before 34 weeks, researchers said.

Those behind the government-funded study indicated that the findings are significant since both the rates of autism and the number of births that are accelerated artificially are on the rise. However, they said that more research is needed to better understand the association and that no change in current practice for inducing or speeding up the labor process is warranted at this time.

“The findings of this study must be balanced with the fact that there are clear benefits associated with induction and augmentation of labor,” said Chad Grotegut, a study author and an assistant professor of obstetrics and gynecology at Duke. “Labor induction, especially for women with post-date pregnancies or medical conditions such as diabetes and high blood pressure, has remarkably decreased the chance of stillbirth.”

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