Well Being

Maternal Age Linked with Autism Risk

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Researchers now say they've confirmed that maternal age is linked with a significantly elevated risk of autism in children. And the father's age may not matter as much as previously thought.

The research from the University of California – Davis was published online today in the February issue of the journal Autism Research. The study is important since it's one of the largest to quantify how each parent's age (separately and together) impacts the risk of autism in children.

The risk of having a child with autism increased by 18% for each five-year increase in maternal age. This means that a mom aged 40 is 50% more likely to give birth to a child later diagnosed with autism than a mom aged 25 to 29 years.

Janie Shelton, lead author of the study and a doctoral student at UC Davis, said:

“This study challenges a current theory in autism epidemiology that identifies the father's age as a key factor in increasing the risk of having a child with autism. 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. Among mothers over 30, increases in the father's age do not appear to further increase the risk of autism.”

Among the births to moms younger than 25, children fathered by a male more than 40 years old were twice as likely to develop autism compared to children whose father was between 25 and 29. However, for moms more than 30 years old, the increased risk of older dads went away.

For the study, researchers used e-records detailing all live births in California between January 1990 and December 1999. The records included both the maternal and paternal ages of parents. To find out which kids developed autism, researchers used records from the state Department of Developmental Services.

All said, the research included approximately 4.9 million births and 12,159 cases of autism.

Researchers aren't yet sure why advanced age affects autism risk. Some theories include maternal antibodies to fetal brain protein or an accumulation of environmental chemicals in the body.

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