A new Swedish study suggests that babies born preterm and early-term births are associated with an increased risk for autism among boys and girls.
Researchers from Icahn School of Medicine at Mount Sinai in New York and Lund University in Sweden looked at 4 million people born between 1973 and 2013.
It also points to a slightly higher prevalence of autism among children who were born just a couple weeks before their due date—what doctors call “early term.”
“Most children born preterm do well,” stressed lead researcher Dr. Casey Crump, a professor at Mount Sinai’s Icahn School of Medicine in New York City.
But this study, he said, strengthens the evidence that early birth is a risk factor for autism.
In addition, preterm babies (born 28 to 32 weeks) had a 40 percent higher chance. Early term babies (born between 37 and 38 weeks) had a 10 to 15 percent higher chance.
“Our findings provide further evidence that gestational age at birth should be routinely included in history taking and medical records for patients of all ages to help identify in clinical practice those born preterm or early term,” the study authors wrote.
“Such information can provide additional valuable context for understanding patients’ health and may facilitate earlier evaluation for ASD and other neuro-developmental conditions in those born prematurely,” they wrote.
Crump said babies and children who were born early should have their development tracked, to catch any delays as soon as possible.
Some children have milder problems with socializing and communicating, while others are profoundly affected—speaking little, if at all, and having repetitive behaviors. Some children have intellectual disabilities, while others have above-average IQs.
The causes of autism are complex and not fully understood, said Dr. Zsakeba Henderson, deputy chief medical and health officer for the nonprofit March of Dimes.
Like Crump, she stressed that most preemies do not develop autism.
But, Henderson said, “these findings do underscore the importance of doing everything we can to prevent babies from being born too early.”
That, she added, includes avoiding labor induction before the 39th week unless there is a medical reason.
It’s not completely clear why early birth can raise autism risk, Crump said. But studies show that preterm infants can harbor markers of body-wide inflammation—a characteristic that may persist into childhood.
Inflammation affecting the brain, Crump said, could be one way preterm birth contributes to autism.
The huge database allowed the researchers to compare siblings—which, Crump said, helps account for genetic and family factors that might affect autism risk.
Even then, the researchers found, preterm and early-term birth were tied to a higher autism risk.
“That suggests a causal relationship,” Crump said.
