With numerous medical conditions, including ejaculatory problems, infections and hormone imbalances, each affecting fertility, the most common cause of male infertility is unhealthy sperm.

Many men may not realize congenital conditions can be a factor, as well. For example, cystic fibrosis (CF) is a genetic disorder that affects at least 30,000 Americans. In other words, you're born with CF—you can't catch it. However, about 1 in 20 people in the United States who carry the abnormal CF gene are unaffected and often unaware they are carriers. For this reason, some men may not discover they have cystic fibrosis until they have trouble conceiving a child.

A gene mutation causes CF, resulting in a buildup of thick, sticky mucus in the lungs, digestive system and other organs, because the gene controls the movement of salt and water in and out of the body's cells. The mucus buildup affects the entire body with a variety of symptoms, such as persistent coughing, frequent lung infections, poor weight gain, bowel problems and, eventually, permanent lung damage. Cystic