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Men's biological clock ticks too

The risk of miscarriage and genetic defects increases with a father's age.

By TOM VALEO
Published August 29, 2006


Women know that the longer the biological clock ticks, the greater the chance of having a baby with Down syndrome. At age 30, a woman has a 1-in-1,000 chance of giving birth to a Down's syndrome baby. By age 45, the odds increase to 1 in 30.

Men, in contrast, tend to assume they can father a healthy baby no matter how old they get.

They should rethink that belief.

Miscarriages are almost three times more common when the father is 35 or older, according to Dr. Karine Kleinhaus of Columbia's Mailman School of Public Health.

In a paper published this month in Obstetrics and Gynecology, Kleinhaus and her colleagues report a clear correlation between the age of the father and the risk of miscarriage.

"In a very young woman, with the father under 25, the risk of miscarriage is about 8 percent," Kleinhaus said. "With an older father, it's more like 24 percent. We think this is related to the quality of sperm, which declines as a man gets older. Sperm loses some of its ability to swim and some of its ability to copy genetic material accurately."

Though a woman is born with all the eggs she will ever have already fully formed, a man produces sperm every day after puberty. By age 45, a man's spermatogonia, which give rise to sperm cells, have divided about 770 times.

The more a cell replicates, the more chances it has to make a copying error and to thus create a mutation, which almost always means trouble.

On top of that, the enzymes that help repair faulty DNA become less efficient with age, so mutant sperm are more likely to get into the game, so to speak.

Miscarriage isn't the only problem facing older fathers.

One study found a correlation between the age of the father and the prevalence of schizophrenia among his children. One child out of every 121 born to men in their late 20s developed schizophrenia, compared to one out of every 47 born to men ages 50-54.

Another study found that older fathers are more likely to have children who are dwarfs, a genetic defect that normally occurs about once every 25,000 births. Older fathers also appear more prone to having children with progeria, a rare genetic disease that causes children to age as much as an 80-year-old would, before the children even reach their teens.

The age of the father also correlates with several congenital heart defects and a certain form of skin cancer.

Even some cases of pre-eclampsia, a complication of pregnancy that causes the mother's blood pressure to soar, may be due to the advanced age of the father. Here, advanced age means 35 and older.

No wonder the American Society for Reproductive Medicine has set the maximum age for semen donors at 40. On top of their growing risk to sire children with genetic defects, men beyond that age are more likely to be infertile.

So what can a man do?

Smoking and heavy drinking appear to damage sperm. Same with certain pesticides. Scientists have found that men who smoke a lot of marijuana tend to have a lower sperm count.

But men are probably better off not worrying too much about this, said Kleinhaus. The risk of these birth defects, after all, is still quite small, even for older parents.

"There's no need to panic," she said. "It's just something to think about. If you're a man over 45 and you want to start having children, you should have all the information."

Freelance writer Tom Valeo writes about medical and health issues. Write to him c/o Pulse, the St. Petersburg Times, P.O. Box 1121, St. Petersburg, FL 33731 or e-mail features@sptimes.com.