Premature birth is linked to an increased risk of autism spectrum disorder (ASD) in both males and females, with those born earliest carrying the highest risk, according to a large and definitive new study in Pediatrics from the Icahn School of Medicine at Mount Sinai. ASD, a disability associated with social, behavioral, and communication challenges, affects nearly one in 54 children in the United States.
The research found that children born between 22 and 27 weeks gestation had nearly four times the risk of developing ASD than children born full-term, between 39 and 41 weeks. Even babies born early-term—at 37 to 38 weeks—carried a 10 percent to 15 percent higher risk of ASD when compared to full-term births.
According to the Centers for Disease Control and Prevention, most children are diagnosed with ASD after the age of four, and boys are more likely to be diagnosed than girls. But an important takeaway from the Mount Sinai study is the need for parents and pediatricians to carefully monitor all premature babies, says the study’s lead author, Casey Crump, MD, PhD, Vice Chair for Research in the Department of Family Medicine and Community Health, and Professor of Epidemiology, Department of Population Health Science and Policy, Icahn Mount Sinai.
Casey Crump, MD, PhD
“Both preterm and early-term births should now be recognized as independent risk factors for autism in both males and females,” say Dr. Crump. “Children born prematurely need early evaluation and long-term follow-up to facilitate early detection and treatment of autism. Hopefully, our findings will help raise awareness of that.”
Dr. Crump and researchers at Lund University in Sweden examined the population records of more than 4 million Swedish individuals across a 30-year period and found the prevalence of ASD was directly related to gestational age. While the risk of ASD in children born between 37 and 38 weeks gestation is relatively modest, he says, the high numbers of children born during that gestational window make it notable.
In reaching their conclusions, the researchers compared siblings within families and were able to control for genetic and environmental factors, which strengthened the link between prematurity and ASD. The researchers also paid attention to these patterns in premature females, a group that had not been studied as extensively as males.
According to Dr. Crump, the study is meant to raise awareness but not alarm parents of premature babies. “Most of these children do very well across their lifespans,” he says.
Yet, “Preterm birth can interrupt or delay the development of all organ systems, such as the cardiovascular system and kidneys, as well as the neurological system,” he adds. For example, the weight of the human brain increases by nearly one-third between 34 and 40 weeks gestation, with significant increases in the volume of white and grey matter. Additional research has shown that the preterm brain is exposed to an inflammatory environment, which could result in a cascade of neuronal injury and alterations that occur prior to birth.
“Parents of children born preterm should be extra careful that their children have close clinical follow-up with physicians who are aware of these issues and can refer them to specialists,” says Dr. Crump. “Earlier detection leads to earlier treatments, which can improve outcomes. Gestational age at birth should certainly be tracked in the medical records to facilitate identification of these people across their life course.”