Senior author Marie Lynn Miranda of the University of Michigan said the findings did not prove cause and effect, but suggested the need for more research, particularly as labor induction and augmentation have been used more frequently in recent years.
"Additional studies are needed to differentiate among potential explanations of the association, such as: underlying pregnancy conditions requiring the eventual need to induce/augment, the events of labor and delivery associated with induction/augmentation, and the specific treatments and dosing used to induce/augment labor such as exogenous oxytocin and prostaglandins," Miranda said in a statement.
Lead author Simon G. Gregory of Duke University analyzed records of all births in North Carolina over an eight-year period and matched 625,042 births with corresponding public school records, which indicated whether children were diagnosed with autism.
The researchers found approximately 1.3 percent of male children and 0.4 percent of female children had autism diagnoses. In both male and female children, the percentage of mothers who had induced or augmented labor was higher among children with autism compared with those who did not have autism.
The findings, published in the Journal of the American Medical Association's Pediatrics, suggested among male children, labor that was both induced and augmented was associated with a 35 percent higher risk of autism, compared with labor that received neither treatment.
This estimated increase in risk accounted for established maternal and pregnancy-related risk factors, such as maternal age and pregnancy complications.
Induced labor alone and augmented labor alone were each associated with increased risk among male children, but only augmentation was associated with increased risk among female children -- this difference requires further investigation, the researchers said.
Gregory said the increased risk associated with induction and augmentation is similar to other known risk factors for developing autism, including a mother being older or a baby being born before 34 weeks of age, the study said.
"The findings must be balanced with the fact that there are clear benefits associated with induction and augmentation of labor," study author Dr. Chad A. Grotegut of Duke Medicine said. "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."
The study authors said the findings did not indicate a change from the current standard of care for using induction and/or augmentation until further research was performed.
Campus cop fatally shoots Texas student during traffic stop
Puzzle-maker slips 'Murdoch Is Evil' into Rupert Murdoch's Sunday Telegraph