Infertility in Men - Male Reproductive System

Causes

More than 90% of male infertility cases are due to low sperm counts, poor sperm quality, or both. The remaining cases of male infertility can be caused by a number of factors including anatomical problems, hormonal imbalances, and genetic defects.

Sperm Abnormalities

Sperm abnormalities can be caused by a range of factors, including congenital birth defects, disease, chemical exposure, and lifestyle habits. (See Risk Factors section.) In many cases, the causes of sperm abnormalities are unknown.

Sperm abnormalities are categorized by whether they affect sperm count, sperm movement, or sperm shape. They include:

• Low Sperm Count (Oligospermia). A sperm count of less than 20 million/mL is considered low sperm. Azoospermia refers to the complete absence of sperm cells in the ejaculate, and accounts for 10 - 15% of cases of male infertility. Partial obstruction anywhere in the long passages through which sperm pass can reduce sperm counts. Sperm count varies widely over time, and temporary low counts are common. Therefore, a single test that reports a low count may not be a representative result.
• Poor Sperm Motility (Asthenospermia). Sperm motility is the sperm's ability to move. If movement is slow, not in a straight line, or both, the sperm have difficulty invading the cervical mucus or penetrating the hard outer shell of the egg. If 60% or more of sperm have normal motility, the sperm is at least average in quality. If less than 40% of sperm are able to move in a straight line, the condition is considered abnormal. Sperm that move sluggishly may have genetic or other defects that render them incapable of fertilizing the egg. Poor sperm motility may be associated with DNA fragmentation and may increase the risk for passing on genetic diseases.
• Abnormal Sperm Morphology (Teratospermia). Morphology refers to shape and structure. Abnormally shaped sperm cannot fertilize an egg. About 60% of the sperm should be normal in size and shape for adequate fertility. The perfect sperm structure is an oval head and long tail.

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