Autism odds rise with older moms

A woman's chance of having a child with autism increases substantially as she ages, but the risk may be less for older dads than previously suggested, according to a new study analyzing more than 5 million births.

"Although fathers' age can contribute risk, the risk is overwhelmed by maternal age," said University of California at Davis researcher Janie Shelton, the study's lead author.

Mothers older than 40 were about 50 percent likelier to have a child with autism than those in their 20s; the risk for fathers older than 40 was 36 percent higher than for men in their 20s.

Even at that, the study suggests the risk of a woman over 40 having an autistic child was still less than 4 in 1,000.

The new research, released yesterday in the February issue of the journal Autism Research, suggests the father's age makes the most difference with young mothers.

Among children whose mothers were younger than 25, autism was twice as common with fathers older than 40 than with dads in their 20s.