Infertility may be caused by more than one factor. Some are easy to find and treat, while others are not. The factor may relate to the woman (65%) or the man (20%). In some cases, no cause can be found in either partner (15%).

The couple’s age can be a factor. For healthy, young couples, the odds are about 20% that a woman will conceive in any one menstrual cycle. This figure starts to decline in a woman’s late 20s and early 30s and decreases even more after age 35 years. A man’s fertility also declines with age, but not as early.

Male factors most often involve problems with the amount or health of the sperm. Abnormal hormone levels may be a cause. Infection or scarring from a sexually transmitted disease (STD) also may be a cause.