Jan. 7 (UPI) -- Parents who were born very prematurely are nearly twice as likely to have children with autism spectrum disorder, according to a study published Thursday by the International Journal of Epidemiology.
Women and men who were born at less than 37 weeks or with low birth weight were more likely to have children diagnosed with autism spectrum disorder than those born at full term and healthy weight, the data showed.
The findings suggest that autism spectrum disorder risk factors can span multiple generations and may help spark further research into the underlying mechanisms of autism risk transmission in families, the researchers said.
"It's already well established that preterm birth and low birth weight of the child are risk factors for autism," study co-author Zeyan Liew said in a statement.
"These adverse characteristics at birth may act as a proxy measure of possible [DNA changes] as a result of harmful prenatal exposures affecting early life growth, which could help explain the multi-generational transmission of disease risk we observed," said Liew, an assistant professor of environmental health sciences at Yale University.
About one in 50 children born in the United States is diagnosed with autism spectrum disorder, the U.S. Centers for Disease Control and Prevention estimates.
ASD is a complex developmental condition in which children experience challenges in social interactions, speech and non-verbal communication and may display repetitive behaviors, according to the American Psychiatric Association.
For their research, Liew and his colleagues analyzed data collected from families in Denmark from 1978 to 2017, linking birth records of parents to the medical records in their offspring.
The prevalence of autism spectrum disorder among children born to parents who experienced complications at birth was nearly twice as high as that for children of parents born at full term and at a healthy weight, the data showed.
Parents' educational achievement, mental health status and their age at the time of pregnancy only contributed "minimally" to autism spectrum disorder risk, the researchers said.
The cause of these potential multi-generational links behind autism spectrum disorder remains unclear.
Liew said it's possible that changes in gene activity in response to environmental stimuli could be inherited across generations without changing the underlying DNA sequences, a phenomenon known as epigenetic inheritance.
In addition, parents who were born prematurely or at low weight may also be more likely to encounter challenges in physical, mental, reproductive or social health in childhood and adulthood, he said.
The findings could fuel new research into understanding how genomic and non-genomic factors that influence early development of parents, and how it can lead to neuro-developmental disorders in their offspring, according to the researchers.
"From previous studies, a lot of the findings that we've seen in Denmark hold up in other countries as well," Liew said.
"This is the first study to show that parental preterm birth and low birth weight might carry some risk for their future offspring as well," he said.