UC Davis study suggests autism risk grows with mother’s advancing age
UC Davis researchers say that a 40-year-old woman's risk of having a child with autism is 50 percent greater than a woman between of 25 and 29 years old.
The researchers' exhaustive new study also found that advanced paternal age is associated with higher autism risk only when the father is older and the mother is under 30.
The study was published today in the February issue of the journal "Autism Research." It is one of the largest population-based studies to report how each parent's age affects the risk of autism.
Advanced parental ages has been known as a risk factor. However, a UC Davis Health System news release states previous research has shown contradictory results on whether it is the mother, father or both who contribute the most to risk.
Janie Shelton, the study's lead author and a doctoral student in the UC Davis Department of Public Health Sciences, said the study challenges a current theory that identifies the father's age as a key factor in increasing the risk.
"It shows that while maternal age consistently increases the risk of autism, the father's age only contributes an increased risk when the father is older and the mother is under 30 years old," said Shelton.
Among mothers over 30, increases in the father's age do not appear to further increase the risk of autism.
Autism is a disorder that affects language and social skills. During the 1990s, according to the press release, the number of California women over 40 who gave birth increased by more than 300 percent.
The researchers obtained records for all births in the state during the 1990s. Understanding the relationship between the age of mothers and fathers and autism is crucial to understanding the cause of autism, researchers said.
The reason that having an older parent places a child at risk for autism is not known, said Irva Hertz-Picciotto, a researcher at the UC Davis MIND Institute and the study's senior author.