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.
Uterine fibroids develop from the smooth muscular tissue of the uterus (myometrium). A single cell divides repeatedly, eventually creating a firm, rubbery mass distinct from nearby tissue. The growth patterns of uterine fibroids vary-they may grow slowly or rapidly, or they may remain the same size. Some fibroids go through growth spurts, and some may shrink on their own. Many fibroids that have been present during pregnancy shrink or disappear after pregnancy, as the uterus goes back to a normal size.
Fibroids range in size from seedlings, undetectable by the human eye, to bulky masses that can distort and enlarge the uterus. They can be single or multiple.
In women who have symptoms, the most common symptoms of uterine fibroids include:
- Heavy menstrual bleeding
- Prolonged menstrual periods- seven days or more of menstrual bleeding
- Pelvic pressure or pain
- Frequent urination
- Difficulty emptying your bladder
- Backache or leg pains
Rarely, a fibroid can cause acute pain when it outgrows its blood supply. Deprived of nutrients, the fibroid begins to die. Byproducts from a degenerating fibroid can seep into surrounding tissue, causing pain and, rarely, fever. A fibroid that hangs by a stalk inside or outside the uterus (pedunculated fibroid) can trigger pain by twisting on its stalk and cutting off its blood supply.
Fibroid location, size and number influence signs and symptoms:
- Submucosal fibroids: Fibroids that grow into the inner cavity of the uterus (submucosal fibroids) are more likely to cause prolonged, heavy menstrual bleeding and are sometimes a problem for women attempting pregnancy.
- Subserosal fibroids: Fibroids that project to the outside of the uterus (subserosal fibroids) can sometimes press on your bladder, causing you to experience urinary symptoms. If fibroids bulge from the back of your uterus, they occasionally can press either on your rectum, causing a pressure sensation, or on your spinal nerves, causing backache.
- Intramural fibroids: Some fibroids grow within the muscular uterine wall (intramural fibroids). If large enough, they can distort the shape of the uterus and cause prolonged, heavy periods, as well as pain and. pressure in extreme cases expanding the uterus so much that it reaches the rib cage.
As many as 3 out of 4 women have uterine fibroids sometime during their lives, but most are unaware of them because they often cause no symptoms. Your doctor may discover fibroids incidentally during a pelvic exam or prenatal ultrasound.
When to see a doctor
See your doctor if you have:
- Pelvic pain that doesn’t go away
- Overly heavy or painful periods
- Spotting or bleeding between periods
- Pain consistently with intercourse
- Enlarged uterus and abdomen
- Difficulty emptying your bladder
Seek prompt medical care if you have severe vaginal bleeding or sharp pelvic pain that comes on suddenly.
By Mayo Clinic Staff
Doctors don’t know the cause of uterine fibroids, but research and clinical experience point to these factors:
- Genetic changes: Many fibroids contain changes in genes that differ from those in normal uterine muscle cells. There’s also some evidence that fibroids run in families and that identical twins are more likely to both have fibroids than nonidentical twins.
- Hormones: Estrogen and progesterone, two hormones that stimulate development of the uterine lining during each menstrual cycle in preparation for pregnancy, appear top promote the growth of fibroids. Fibroids contain more estrogen and progesterone receptors than normal uterine muscle cells do. Fibroids tend to shrink after menopause due to a decrease in hormone production.
- Other growth factors: Substances that help the body maintain tissues, such as insulin like growth factor, may affect fibroid growth.