Infertility is defined as the inability for a couple to become pregnant after a year of unprotected intercourse. The male partner, the female partner, or both may have a fertility problem. A person who is infertile has a reduced ability to have a child. It usually doesn't mean a person is sterile — that is, physically unable ever to have a child.
For many couples, infertility is a crisis. Fertility problems often come with feelings of guilt or inadequacy. Up to 15% of all couples are infertile, but only 1% to 2% are sterile. Half of couples who seek help can eventually bear a child, either on their own or with medical assistance. Men and women are equally likely to have a fertility problem. In about 1 in 5 infertile couples, both partners have contributing problems, and in about 15% of couples, no cause is found after all tests have been done, called "unexplained infertility."