What is infertility?

Most experts define infertility as not being able to get pregnant after at least one year of trying. Women who are able to get pregnant but then have repeat miscarriages are also said to be infertile.

Pregnancy is the result of a complex chain of events. In order to get pregnant:

• A woman must release an egg from one of her ovaries. (ovulation).

• The egg must go through a fallopian tube toward the uterus (womb).

• A man's sperm must join with (fertilize) the egg along the way.

• The fertilized egg must attach to the inside of the uterus (implantation).

Infertility can result from problems that interfere with any of these steps.

Is infertility a common problem?

About 12 percent of women (7.3 million) in the United States aged 15-44 had difficulty getting pregnant or carrying a baby to term in 2002, according to the National Center for Health Statistics of the Centers for Disease Control and Prevention.

Is infertility just a woman's problem?

No, infertility is not always a woman's problem. In only about one-third of cases is infertility due to the woman (female factors). In another one third of cases, infertility is due to the man (male factors). The remaining cases are caused by a mixture of male and female factors or by unknown factors.

What causes infertility in men?

Infertility in men is most often caused by:

• problems making sperm -- producing too few sperm or none at all
• problems with the sperm's ability to reach the egg and fertilize it -- abnormal sperm shape or structure prevent it from moving correctly

Sometimes a man is born with the problems that affect his sperm. Other times problems start later in life due to illness or injury. For example, cystic fibrosis often causes infertility in men.