Oligospermia is also known as a low sperm count or oligozoospermia. In oligozoospermia there are fewer sperm cells in the ejaculate than normal. Oligospermia is generally defined as less than 20 million spermatozoa per one ml of ejaculate.

Oligospermia is one of the main causes of male infertility or sub-fertility. Sub-fertility is a reduced ability to achieve a pregnancy while infertility is defined as the complete inability to produce a pregnancy after about one year of unprotected sexual activity.

Oligospermia can be the result of many factors, some are permanent and some are reversible. Causes of oligospermia include an obstruction of the normal flow of sperm due to such conditions as testicular trauma and vasectomy. Oligospermia may also result from scarring due to surgery on the male reproductive system or from infection and sexually transmitted diseases.

A decrease in sperm production is another cause of oligospermia. This can be due to such conditions as varicoceles, hormonal disorders, diseases of the testicles, and obesity. Other causes of oligospermia include stress, smoking, drug or alcohol use, some medications, exposure to some toxins, malnutrition, and being underweight. Some sexually transmitted disease, such as chlamydia, and gonorrhea can also result in oligospermia.

The main symptoms and complications of oligospermia are sub-fertility or infertility. There are also a variety of symptoms of underlying causes of oligospermia, such as sexually transmitted diseases and hormonal disorders. For more details on complications and symptoms, refer to symptoms of oligospermia.

Making a diagnosis of oligospermia includes taking a medical and sexual history and completing a general physical examination as well as an exam of the penis and testicles. Diagnostic testing includes performing a semen analysis, which examines the ejaculate for the amount and quality of semen and sperm.

Testing also includes performing lab tests to determine if an infection or sexually transmitted disease is present and the type of infecting organism. Other tests may be done to rule-out other potential causes of oligospermia, such as a hormonal disorder.

Because there may be no symptoms before a man attempts to get a woman pregnant, some men may be unaware of oligospermia. This can result in a missed or delayed diagnosis.