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HOW DO SPERM ABNORMALITIES CONTRIBUTE TO MALE INFERTILITY?
More than 90% of male infertility cases are due to low sperm counts, poor sperm quality, or both. In 30% to 40% of cases of sperm abnormalities, the cause is unknown. It may be the end result of one or a combination of factors that include chronic illness, malnutrition, genetic defects, structural abnormalities, and environmental factors. Partial obstruction anywhere in the long passages through which sperm pass can reduce their sperm counts. In one study, obstruction was believed to be a contributing factor in over 60% low sperm count cases. Obstruction itself can be caused by many factors. [ See What Are the Causes of Sperm Obstruction in Male Infertility?, Below. ]
General Problems with Sperm Production and Quality
Defining Sperm Abnormalities. Sperm abnormalities are categorized by whether they effect sperm count, sperm quality, or both:
|
Category |
Medical Name |
Description / Comment |
|
Low sperm count |
oligospermia |
Sperm count is considered low when it is less than 10 million sperm/mL of semen. There are literally dozens of causes of temporary and permanent low sperm count. |
|
No sperm |
azoospermia |
Complete absence of sperm. This is relatively rare, affecting less than 1% of all men and 10% to 15% of infertile men. This may be due to obstruction or production failure of sperm in the testes (Sertoli cell-only syndrome), which can be caused by infections such as mumps, genetic disorders, radiation , or exposure to chemicals. |
|
Low-quality sperm |
dysspermia |
Quality is determined by the sperm's motility (its ability to move) or its morphology (its shape and structure). The quality of the sperm is often more significant than the count. |
|
No semen production |
aspermia |
Ejaculation does not emit any semen. |
One study reported the fertilization rates in men with one or more defects (sperm count, motility, or morphology) as follows:
- 71% for men with a single defect.
- 50% for a double defect.
- 39% for triple defects.
Low Sperm Count. Sperm count is now considered to be below normal (oligospermia) if it is less than 10 million/mL. In the past, a sperm count of less than 40 million/mL in the ejaculate was believed to cause infertility. Now, however, if the woman is fertile and young, a count as low as 10 million can often accomplish conception over time, even without treatment. In fertilization clinics, men with low sperm counts report fertilization rates of about 30%, while those with average sperm counts have rates between 60% and 80%.
It should be noted that 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.
Sperm Motility. 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 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 Morphology. 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 number of variations:
- A very large round head. (In one study, if 14% or more of sperm had round enlarged heads, the chances for pregnancy fell to about 20%. Such an abnormality indicates early unraveling of genetic material. In the same study, pregnancy was impaired if 7% or more of sperm had abnormalities in the acrosomes causing them to release enzymes prematurely.)
- An extremely small pinpoint head.
- A tapered head.
- A crooked head.
- Two heads.
- A tail with kinks and curls.
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