Uterine fibroids are noncancerous growths of the uterus that often appear during childbearing years. Also called leiomyomas (lie-o-my-O-muhs) or myomas, uterine fibroids aren't associated with an increased risk of uterine cancer and almost never develop into cancer.

Fibroids range in size from seedlings, undetectable by the human eye, to bulky masses that can distort and enlarge the uterus. You can have a single fibroid or multiple ones. In extreme cases, multiple fibroids can expand the uterus so much that it reaches the rib cage and can add weight.

Many women have uterine fibroids sometime during their lives. But you might not know you have uterine fibroids because they often cause no symptoms. Your doctor may discover fibroids incidentally during a pelvic exam or prenatal ultrasound.

Symptoms

Many women who have fibroids don't have any symptoms. In those that do, symptoms can be influenced by the location, size and number of fibroids.

In women who have symptoms, the most common signs and symptoms of uterine fibroids include:

• Heavy menstrual bleeding
• Menstrual periods lasting more than a week
• Pelvic pressure or pain
• Frequent urination
• Difficulty emptying the bladder
• Constipation
• Backache or leg pains

Rarely, a fibroid can cause acute pain when it outgrows its blood supply, and begins to die.

Fibroids are generally classified by their location. Intramural fibroids grow within the muscular uterine wall. Submucosal fibroids bulge into the uterine cavity. Subserosal fibroids project to the outside of the uterus.

When to see a health care provider

See your health care provider if you have:

• Pelvic pain that doesn't go away
• Overly heavy, prolonged or painful periods
• Spotting or bleeding between periods
• Difficulty emptying your bladder
• Unexplained low red blood cell count (anemia)

Seek prompt medical care if you have severe vaginal bleeding or sharp pelvic pain that comes on suddenly.

Read more about the causes, risk factors, prevention and treatment.

This article is written by Mayo Clinic Staff. Find more health and medical information on mayoclinic.org.

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