Infertility is defined as a couple's failure to conceive a child after one year of regular sexual intercourse without birth control. In about 40 percent of all cases of infertility, the problem lies with the man; in 60 percent, it lies with the woman or with both partners.

Infertility is not sterility. The term infertility implies that the condition can be treated and reversed -- that it may be a temporary problem. The term sterility is applied to a permanent, irreversible inability to have children.

Recent research has shown that a woman's fertility drops off significantly between the ages of 31 and 35 and continues to decline thereafter until menopause, when it ceases altogether. A man's fertility also declines after the age of 40, although men can remain fertile until old age. In this article, we will examine the causes of both male and female infertility, as well as infertility diagnosis and treatment.

Causes of Male Infertility

One of the major causes of male infertility is a low sperm count. It is measured by the number of active sperm present in a milliliter (there are approximately five milliliters in one teaspoon) of semen (the fluid ejected from the penis during intercourse). An average sperm count is 90 million or more sperm per milliliter. A count of at least 40 to 60 million is thought to be necessary for fertilization; when the count is less than 20 million, it is unlikely that the man can father a child (although, since only one sperm is needed to fertilize an egg, it is still possible).

A low sperm count can be caused by low levels of testosterone (the male sex hormone); by exposure to chemicals, pesticides, or radiation; by engaging in sexual intercourse too frequently, which depletes the sperm supply too quickly; and by heat (which slows sperm production) generated by wearing tight underwear or pants, sitting for long periods in hot cars or trucks, or working near ovens and kilns.

Infertility can also result if sperm cannot propel themselves through the female reproductive tract to reach the egg, or if sperm are irregularly shaped (only sperm with oval-shaped heads can fertilize an egg).

In addition to problems with the sperm themselves, male infertility can be caused by any obstruction in the tubes that convey the sperm from the testes (the male sex organs where sperm are produced) to the penis. Infertility may also be caused by varicose veins in the scrotum (the pouch containing the testes), perhaps because the increased blood flow in these swollen veins brings extra heat to the area, or by a local infection or injury; the infertility problem will probably reverse itself when the condition is corrected.

In addition, surgical removal of part of the prostate gland (one of the organs in which most of the fluid in semen is produced), as well as the use of certain drugs for high blood pressure, can lead to retrograde ejaculation (a disorder in which the semen is passed backward into the bladder, to exit with the urine, rather than out through the penis).

Causes of Female Infertility

A woman may be infertile because of a variety of conditions. It may be that she is not ovulating (releasing an egg each month); this is true in about 25 percent of all cases of female infertility. The fallopian tubes (through which the eggs travel on their way from the ovaries to the uterus) may be obstructed, often as a result of pelvic inflammatory disease (PID), which irritates the tubes and causes scar tissue to form. PID can develop as a reaction to an STD or an infection of the lower reproductive tract.

Endometriosis (the displacement of tissue from the uterine lining to elsewhere in the body) may also cause the formation of scar tissue that blocks the fallopian tubes. An imbalance of the female hormones estrogen and progesterone or of other hormones secreted from the pituitary or thyroid glands can interfere with the reproductive cycle. A cervix that creates an environment that in some way prevents sperm from surviving may also be the cause of the infertility.

Now let's consider the diagnosis and treatment of infertility. It's in the next section.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.