Large study strengthens link between autism, preterm birth

By Charles Q. Choi for

Premature birth is tied to an increased chance of having autism, according to the largest study yet to examine the connection. And premature birth itself — rather than unrecognized genetic or environmental factors — seems to underlie the association.

The findings suggest that infants born prematurely need early evaluation and long-term follow-up to support the timely detection and treatment of autism, experts say.

“We know that early intervention can make a huge difference in later outcome, and more effective interventions are increasingly available,” says April Benasich, professor of developmental cognitive neuroscience at Rutgers University in Newark, New Jersey, who did not participate in this study.

Previous research suggests that babies born preterm — before the 37th week of pregnancy — have a roughly 30 percent higher chance of having autism than do those born full-term. Nearly 11 percent of births worldwide are premature, and more than 95 percent of these babies survive with modern neonatal care.

“Our prior work has shown that most children who were born preterm survive into adulthood without neurodevelopmental disorders or other chronic health problems,” says lead investigator Casey Crump, professor and vice chair of research in the family medicine and community health department at the Icahn School of Medicine at Mount Sinai in New York City.

But researchers have long debated whether preterm birth contributes to autism or whether both conditions might share genetic or environmental influences. It was also unclear if the link shows a sex bias, or if it extends to early-term birth — during weeks 37 and 38 of pregnancy — which is roughly three times more common than preterm birth.

In the new study, researchers scoured national healthcare and birth registries to analyze data for more than 4 million people born in Sweden between 1973 and 2013.

“I was bowled over by the cohort size,” Benasich says.

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