Over 4.5 million American men and women -- or roughly 1 out of 5 (15-20%) couples -- fail when attempting their first pregnancy. In these couples, about half of the men will have a significant abnormality that makes them unable to father children.

Male infertility may be caused by abnormalities in the testes or other areas of the male reproductive tract, as well as immune system defects. Yet the most common cause of male infertility is disordered sperm production. Fortunately, new diagnostic tests are available to help define some of the more obscure causes of male infertility. Specialists should perform an initial screening of the male partner whenever a couple complains of infertility.