Possible new autism risk factors found

New autism risks found

Children who are firstborn or breech or whose mothers are 35 or older when giving birth are at significantly greater risk for developing an autism spectrum disorder, University of Utah School of Medicine researchers have reported in a new study with Utah children.

Researchers showed that women who give birth at 35 or older are 1.7 times more likely to have a child with an autism spectrum disorder (ASD), compared with women between the ages of 20 and 34. Children diagnosed with ASD also were nearly 1.8 times more likely to be the firstborn child, the researchers found.

Although they didn't identify a causal relationship between breech births and autism, children diagnosed with the disorder were more than twice as likely to have been a breech presentation, meaning they were not born head first.

“The results of this study give us an opportunity to look more closely at these risk factors for children across the autism spectrum, and not only those diagnosed with autism,” says first author Deborah A Bilder, MD, assistant professor of psychiatry. “This shows that further investigation of the influence of prenatal factors is warranted.” The researchers also identified a small but significant relationship between the increased duration of education among mothers of those children.

Further investigation would be needed to understand how these three risk factors may relate to ASD. But a possible explanation for the correlation of firstborn children might be that parents are reluctant to have a second child if the first is diagnosed with ASD. A possible interpretation of increased risk associated with advanced maternal age is that changes in genes occurring over time may contribute to autism spectrum disorders. The association found between breech presentation and ASD most likely indicates a shared cause, such as neuromuscular dysfunction. The vast majority of children born breech, however, are healthy.

The study was published April 27 in the online issue of the journal Pediatrics.

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