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Experts note that even with the higher chance, preterm babies have only a 6 percent rate of autism. Jill Lehmann Photography/Getty Images
  • Researchers say babies who are born preterm may have a higher chance of developing autism.
  • They say their findings add to previous research that has concluded that genetic and environmental factors can play a role in autism risk.
  • Researchers add that babies born preterm still only have a 6 percent rate of autism, so their findings should be used as a diagnostic tool to help with early intervention.

Babies born preterm or early term may have as much as a four times higher chance of autism spectrum disorder (ASD) than babies born full-term, a new Swedish study suggests.

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.

They reported that extremely preterm babies (born before 28 weeks) had four times the chance of developing autism than full-term babies.

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.

The study authors didn’t speculate as to why preterm birth presents a higher chance of autism, but previous research indicates that a combination of genetic and environmental factors both play a part.

For instance, recent studies have discovered 102 separate genes linked to ASD. Many of these genes also have a large role in early brain development.

“Having a premature baby, having complications during pregnancy (such as bleeding or high blood pressure), exposure to endocrine-disrupting chemicals (for example, through food, cosmetics, or water), and carrying multiples all appear to increase the risk of autism,” Emily Papazoglou, PhD, a board certified clinical neuropsychologist based in Georgia, told Healthline.

“We do not yet understand why these factors increase the risk of a child having autism,” she said, “and many children are born healthy after being exposed to one or more of these risk factors.”

One thing is certain.

Vaccines do not play a role in whether children develop autism, according to several large studies.

One study of a half-million people found that children who had a sibling with autism were 14 times more likely to have autism than the general population — again indicating genetic factors at play.

Increases in autism diagnoses over the years are instead driven by a better understanding of early autism signs and symptoms as well as more common screenings for it, research shows.

Having a preterm baby does not mean your child will develop autism. Even extremely preterm babies in the study only had a 6 percent rate of autism.

That said, if your child is born prematurely, screenings and early interventions can help ensure your child gets the best possible support if they need it.

“We know that the sooner intervention is implemented for children with autism, the better outcomes are. Intervention before the age of 5 — and even more ideally in the early toddler years — seems to be particularly crucial,” Papazoglou said.

“The importance of early identification and immediate implementation of appropriate interventions cannot be overstated,” added Dana Sciullo, a pediatric occupational therapist based in Pennsylvania who specializes in children with autism.

“Around the age of 2, children’s brains undergo significant growth and neural connection formation during which the brain is at its highest ‘neural plasticity’ or potential for change,” Sciullo told Healthline.

“In my own practice, I have seen children who were diagnosed early and received intense intervention grow up to have no obvious signs of autism. This is not always the case, but early treatment invariably has a positive effect on the outcome of the child,” she said.