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.
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Why do older men have higher odds of fathering children with autism? The most prominent hypothesis is that the sperm of older men has accumulated many spontaneous mutations that the men pass along to their children.
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Some studies have suggested that a woman’s chance of having a child with autism also increases steadily with age. The number of de novo mutations in egg cells increases with age, although to a lesser degree than it does in sperm. As with men, women who have autism traits may have children late. However, a comprehensive analysis found that for a woman over age 35, the chance of having a child with autism is lower than for younger women.
That study also suggested that women under age 25 are more likely to have a child with autism than older women. The finding echoed that of several other studies that reported that teenage mothers also have increased odds of having a child with autism.
