Older men and women are more likely than young ones to have a child with autism, according to multiple studies published in the past decade. Especially when it comes to fathers, this parental-age effect is one of the most consistent findings in the epidemiology of autism.
The link between a mother’s age and autism is more complex: Women seem to be at an increased risk both when they are much older and much younger than average, according to some studies.
Nailing down why either parent’s age influences autism risk has proved difficult, however.