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Low Sperm Count
A normal sperm count is considered to be 20 million/mL. A lower than normal sperm count can be caused by a variety of defects, which usually occur later in sperm development, since most men have an adequate number of sperm–creating germ cells. When the cause is not known, which occurs in half the cases, the condition is known as idiopathic oligospermia.
Sperm count may vary widely over time as well, so a single test that reports a low count may not be a representative result. Temporary low counts can be caused by many conditions, including high fever, stress, various drugs, chemotherapy, environmental toxins, overheating, and lack of sleep.Complete failure of the testes to produce any sperm is relatively rare, affecting less than 5% of infertile men. Low counts do not preclude fertilization if the woman is fertile. In the past, less than 40 million sperm per cubic centimeter (cc) in the ejaculate was believed to cause infertility. Now, however, if the woman is fertile and young, it is believed that a sperm count as low as 10 million cc can accomplish conception over time, even without treatment.
The quality of the sperm is often more significant than the count. Sperm motility is the ability to move. If motility is slow, not straight forward, or both, the sperm have difficulty invading the cervical mucous or penetrating the hard outer shell of the egg. If 60% or more of sperm have normal motility, then 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 also have other defects that render them incapable of fertilizing the egg. Sperm motility can be affected by infections in the semen, semen that is too thick, or a poor environment within the epididymis.
Morphology refers to the shape and structure of an object. Morphology may be even more important than count or motility in determining potential fertility. Abnormally shaped sperm cannot fertilize an egg. About 60% of the sperm should be normal in size and shape for adequate fertility. The perfect structure is an oval head and long tail. Abnormally shaped sperm may include a very large round head, an extremely small pinpoint head, a tapered head, a crooked head, two heads, or a tail with kinks and curls. Such an abnormality indicates early unraveling of genetic material.
Germ–cell aplasia is the defective development of the sperm–producing germ cells. It may be caused by genetic defects or structural problems that occur during fetal development. Problems with Semen A reduced amount of ejaculated semen (less than 0.5 millimeters per sample) may be caused by inflammation of the seminal vesicles (the glands that produce semen) or a structural abnormality in the tubes transporting the sperm. Semen that does not liquefy properly can result from infections or from abnormal immune factors.