Description: The failure in a women to conceive or in a man to induce conception.

Persons most commonly affected: Women's fertility drops off significantly between the ages of 31 and 35 and continues to decline thereafter until menopause, when it ceases. A man's fertility also declines after the age of 40, although men can remain fertile until old age.

Organ or part of body involved: Reproductive system.

Symptoms and indications: Inability to become pregnant after one year of regular sexual intercourse without birth control. A range of emotional reactions by either or both members of the couple related to childlessness. (In general, such reactions are greater among childless couples. Having a single child tends to blunt the depth of emotional problems.

Causes and risk factors: Male Infertility -- a low sperm count which may 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, it can be caused by any obstruction in the tubes that convey the sperm from the testes to the penis, varicose veins in the scrotum, or by a local infection or injury. Certain drugs used to treat hypertension, arthritis, and digestive disease, as well as chemotherapy drugs are associated with sperm production problems and infertility. Female Infertility -- may be she is not ovulating, the fallopian tube may be obstructed, imbalance of the female hormones estrogen and progesterone or of other hormones secreted from the pituitary or thyroid glands can interfere with the reproduction cycle.

Prevention: Most types of infertility cannot be prevented. Smoking has been linked to low sperm counts and sluggish sperm movement in men, and an increase in miscarriage in women. Alcohol (especially binge drinking or chronic abuse), affects the fertility of both men and women trying to conceive either naturally or through infertility treatments. Alcohol is toxic to sperm; it reduces sperm counts, can interfere with sexual performance, disrupt hormone balances and increase the risk of miscarriage. While the inability to conceive can place stress on a relationship, avoid the temptation to relieve the stress using alcohol. Other useful methods include meditation, relaxation, moderate physical activity and yoga. A well-balanced diet includes carbohydrates, protein and fibre. All women should increase folic acid intake (found in green leafy vegetables, fruit, cereals, but also available as supplements) prior to and during the first three months of pregnancy, to reduce the risk of neural tube defects such as spina bifida. Excessive exercise can lead to menstrual disorders in women and affect sperm production in men due to the heat build-up around the testicles. Avoid environmental poisons and hazards such as pesticides, lead, heavy metals, toxic chemicals, and ionising radiation. Check with your doctor that any medication or herbal remedies (prescribed or over-the-counter) that you may be taking do not affect fertility. Give up recreational drugs such as marijuana and cocaine as these have been linked to low sperm counts in men and infertility in women. Limit sex partners and use condoms to reduce the risk of getting a sexually transmitted disease (STD). STDs that go undetected and untreated can damage the reproductive system and cause infertility. If you think you may have an STD, get treatment promptly to reduce the risk of damage to your reproductive system. Maintain a body weight close to the ideal for your height to reduce the possibility of hormone imbalances.