Inducing labour does not appear to increase the baby’s odds of autism, a study suggests.

Researchers examined data on more than 1.3 million births in Sweden and found about 3.5 per cent of babies born after induction were diagnosed with autism by age 20, compared with 2.5 per cent of other infants. This translates into a roughly 19 per cent greater risk of autism with induced labour, which is statistically significant.

But when researchers took a closer look just at sibling pairs with one baby that arrived after induction and another that did not, they no longer found any link between induced labour and autism risk. The results from nearly 700,000 siblings suggest that any elevated autism risk associated with labour induction is actually due to other factors such as genetics or medical issues experienced by individual women, said lead study author Anna Sara Oberg of Harvard University in Boston.

Results suggest any elevated autism risk associated with labour induction is actually due to other factors

“The association observed between unrelated individuals may be a result of confounding factors, and not a causal effect of labour induction on the risk of autism spectrum disorder.”

Oberg and colleagues reviewed data on all live births in Sweden from 1992 to 2015. Overall, about 11 per cent of these deliveries were induced, the researchers reported online in JAMA Pediatrics.

Labour induction was more common when mothers were older, obese, hypertensive, or diabetic. The mother’s country of origin, education level and smoking status early in pregnancy did not appear to impact whether they would have an induced labour.

One limitation of the study is that it did not examine various types of labour induction, which can include a variety of medications and procedures to help labour begin and progress.

The findings from the current study also run counter to a large 2013 study of US babies that did link labour induction to a greater risk of autism, Oberg noted.