Scientists have now called for more research to explain the difference with doctors saying induced labour is "safe, necessary and could save a baby's life".
The study of 625,000 births in North Carolina showed 13 out of every 1,000 boys born, and four per 1,000 girls, developed autism.
Conflicting evidence on autism & induced labour
However, the rate was a third higher in boys when their mother needed drugs to induce or assist the pregnancy.
Study lead Professor Simon Gregory, of Duke University, explained that there has been a lot of conflicting evidence on autism and inducing labour, but this study was the largest to look at the issue.
"We don't want mothers to say, 'Under no circumstances do I want to be induced because I don't want a kid with autism'. That would be plain wrong," he said.
"We've found an association and more research is needed. This allows us to focus on the factors around birth that may affect autism and how it develops."
Autism is thought to be caused by a combination of family, or genetic, risk and conditions in the womb and early life while the child is developing.
Underlying genetic factors
Researchers said that two cases of autism in every 1,000 births might be prevented by stopping induction. However, they warned this would come at significant cost as the procedure could be life-saving.
Labour is often induced when the pregnancy has gone on too long and the mother has missed the due date, normally by at least a week.
Carol Povey, of the National Autistic Society, said: "Autism is a complex condition and is thought to be the result of many different underlying physical and genetic factors. Its exact causes are still being investigated.
"The scientists who conducted this study acknowledge that further research is required before any hard and fast conclusions can be drawn.
"It's therefore important that people do not jump to conclusions about this study and its implications."
For more information visit: www.dukehealth.org/health_library/news/inducing-and-augmenting-labor-may-be-associated-with-increased-risk-of-autism