A child's risk for autism rapidly increases with mothers who are over the age of 30, a recent study indicated.
Researchers behind the verdict, published in the International Journal of Epidemiology, note that older parents are more likely to have a child who develops an autism spectrum disorder (ASD) than younger parents, but this risk varies between mothers and fathers.
For fathers, the associated risk gradually increased as they aged. Among women giving birth before the age of 30, the risk of ASD was so low that it was deemed insignificant. But for babies born to mothers aged 30 and older, the chance of developing ASD noticeably accelerated with the mother's age.
About 1 in 68 children is identified with ASD, and it is almost 5 times more common among boys (1 in 42) than among girls (1 in 189), according to the Centers for Disease Control and Prevention (CDC).
To better identify more ASD cases than in previous studies, study leader Brian K. Lee and colleagues analyzed a large population registry sample of 417,303 children born in Sweden - a country with socialized health care - between 1984 and 2003, adjusting for other possible factors.
"The absolute risk of having a child with ASD is still approximately 1 in 100 in the overall sample, and less than 2 in 100 even for mothers up to age 45," Lee, an assistant professor in the Drexel University School of Public Health, said in a statement.
Although the absolute risk of autism does rise rapidly, the results show that the relative risk is still fairly low.
Multiple elements could explain the heightened risk associated with maternal age. Factors such as complications during pregnancy or environmental risk factors specifically linked to women over 30 may play a role. Additionally, older mothers may be more inclined to seek diagnosis for their developmentally troubled children. The CDC notes that parents who have a child with ASD have a 2 percent to 18 percent chance of having a second child who is also affected.