Some fertility experts say men have their own biological clock and shouldn't be too cavalier about postponing children.
The New York Times says recent studies show men in their mid- to late 40s have an increased risk of fathering children with genetic abnormalities, including autism and schizophrenia.
The newspaper said analyses of sperm samples has found changes as men age, including increased fragmentation of DNA.
"Obviously there is a difference between men and women; women simply can't have children after a certain age," said Dr. Harry Fisch, director of the Male Reproductive Center at New York-Presbyterian Hospital/Columbia University Medical Center. "But not every man can be guaranteed that everything's going to be fine."
Fisch, author of "The Male Biological Clock, said, "Fertility will drop for some men, others will maintain their fertility but not to the same degree, and there is an increased risk of genetic abnormalities."
Copyright 2007 by United Press International
Explore further: Choking air, melting glaciers: how global warming is changing India