Induction of labour does not appear to be associated with an increased risk of autism spectrum disorders in children, according to a new study.

Researchers say the finding should provide some reassurance to patients after a study published three years ago did find such an association. That study's authors pointed out in 2013 that the association might not be causal.

But the study garnered enough public attention that obstetricians said some of their patients were worried about being induced.

Labour is sometimes induced through mechanical or pharmacological methods when doctors fear that waiting might endanger the health of the baby or the mother.

The new study, which was led by the Harvard T.H. Chan School of Public Health, was aimed at figuring out whether the induction of labour really caused an increased risk of autism.

To do that, researchers studied over one million live births in Sweden from 1995 to 2005. They followed the children through 2013, looking for any evidence of neuropsychiatric problems.

Study 'should provide reassurance'

When they compared individuals who weren't related to each other, researchers found an association between labour induction and autism risk, just as the 2013 study did.

But when they compared siblings born to the same mother — when one child was delivered after induced labour and the other wasn't — the association disappeared.

"Overall, these findings should provide reassurance to women who are about to give birth, that having their labour induced will not increase their child's risk of developing autism spectrum disorders," said one of the researchers, Brian Bateman, anesthesiologist and associate professor of anesthesia at Massachusetts General Hospital and Brigham and Women's Hospital, Harvard Medical School.

Another of the researchers, Anna Sara Oberg, noted that the findings relate to the risks associated with labour induction on its own, rather than the specific method or medication used.

The study was published online Monday in JAMA Pediatrics.