Health risks associated with mother's age are more generally known, which is why experts are working to make more people aware that the father's age increases risk too. One of those experts is Harry Fisch, MD, a specialist in male fertility and professor at Columbia University Medical Center at New York Presbyterian Hospital.

"It has long been known that a woman's chance of having a baby with Down syndrome rises dramatically after age 35, but it had been thought that the man's age had nothing to do with it. Now we know that this is false--men also have a higher likelihood of fathering a Down syndrome baby as they get older," writes Dr. Fisch in his book The Male Biological Clock.

If you're nearing your 40s and thinking of having kids, remember that a risk factor only means that something has an above-average chance of happening--not that it will definitely happen. The majority of older fathers and mothers have healthy children, and you can take steps to lower certain risks. Consult your doctor if you have concerns.

Positive actions

Is there any way to slow the biological clock and boost the chances of fathering a healthy child? It's a myth that the quality and quantity of sperm can't be improved, according to Dr. Fisch. He suggests that men:

• Get regular, moderate exercise
  
• Eat a nutritious diet
  
• Avoid things that can damage sperm, including cigarettes, anabolic steroids and hot tubs