Infertility Fact Sheet

What causes infertility in men?

Infertility in men is most often caused by:

A problem called varicocele (VAIR-ih-koh-seel). This happens when the veins on a man's testicle(s) are too large. This heats the testicles. The heat can affect the number or shape of the sperm.
Other factors that cause a man to make too few sperm or none at all.
Movement of the sperm. This may be caused by the shape of the sperm. Sometimes injuries or other damage to the reproductive system block the sperm.
Sometimes a man is born with the problems that affect his sperm. Other times problems start later in life due to illness or injury. For example, cystic fibrosis often causes infertility in men.

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What increases a man's risk of infertility?

A man's sperm can be changed by his overall health and lifestyle. Some things that may reduce the health or number of sperm include:

Heavy alcohol use
Drugs
Smoking cigarettes
Age
Environmental toxins, including pesticides and lead
Health problems such as mumps, serious conditions like kidney disease, or hormone problems
Medicines
Radiation treatment and chemotherapy for cancer
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What causes infertility in women?

Most cases of female infertility are caused by problems with ovulation. Without ovulation, there are no eggs to be fertilized. Some signs that a woman is not ovulating normally include irregular or absent menstrual periods.

Ovulation problems are often caused by polycystic ovarian syndrome (PCOS). PCOS is a hormone imbalance problem which can interfere with normal ovulation. PCOS is the most common cause of female infertility. Primary ovarian insufficiency (POI) is another cause of ovulation problems. POI occurs when a woman's ovaries stop working normally before she is 40. POI is not the same as early menopause.

Less common causes of fertility problems in women include:

Blocked fallopian tubes due to pelvic inflammatory disease, endometriosis, or surgery for an ectopic pregnancy
Physical problems with the uterus
Uterine fibroids, which are non-cancerous clumps of tissue and muscle on the walls of the uterus.