Researchers at Michigan State University have discovered a connection between length of pregnancy and the severity of autism symptoms.
The research suggests normal term children born with autism have less severe symptoms than children with autism who are born pre-term or several weeks late.
Researchers also say that children with autism who were born either preterm or post-term are more prone to self-injury compared with children with autism who are born on time.
The research appears online in the Journal of Autism and Development Disorders.
While it is not yet clear why there is an increase in symptoms of autism, Tammy Movsas, M.D., a postdoctoral epidemiology fellow, believes the reasons may be tied to some of the underlying causes of why a child is born preterm (prior to 37 weeks) or post-term (after 42 weeks) in the first place.
“We think about autism being caused by a combination of genetic and environmental factors,” she said. “With preterm and post-term babies, there is something underlying that is altering the genetic expression of autism.”
“The outside environment in which a preterm baby continues to mature is very different than the environment that the baby would have experienced in utero. This change in environment may be part of the reason why there is a difference in autistic severity in this set of infants.”
Researchers utilized an online database compiled by Kennedy Krieger Institute at Johns Hopkins University of nearly 4,200 mothers — with children with ASD ages 4-21 — between 2006 and 2010. It divided the data on births into four categories: very preterm (born prior to 34 weeks); preterm (34 to 37 weeks); standard (37 to 42 weeks); and post-term (born after 42 weeks).
The mothers were required to complete a pair of questionnaires regarding the symptoms of their children, and the results revealed very preterm, preterm and post-term children with autism had significantly higher screening scores for autism spectrum disorder than those born full term.
“The findings point to the fact that although autism has a strong genetic component, something about pregnancy or the perinatal period may affect how autism manifests,” said Nigel Paneth, M.D., an MSU epidemiologist who worked with Movsas on the paper.”
“This adds to our earlier finding that prematurity is a major risk factor for autism spectrum disorder and may help us understand if anything can be done during early life to prevent or alleviate autism spectrum disorder.”