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 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.
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.
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 to 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.
There are few known risk factors for uterine fibroids, other than being a woman of reproductive age. Other factors that can have an impact on fibroid development include:Heredity. If your mother or sister had fibroids, you’re at increased risk of developing them.
Heredity. If your mother or sister had fibroids, you’re at increased risk of developing them.Race. Black women are more likely to have fibroids than women of other racial groups. In addition, black women have fibroids at younger ages, and they’re also likely to have more or larger fibroids. Other factors. Onset of menstruation at an early age, having a diet higher in red meat and lower in green vegetables and fruit, and drinking alcohol, including beer, appear to increase your risk of developing fibroids.
Although uterine fibroids usually aren’t dangerous, they can cause discomfort and may lead to complications such as anemia from heavy blood loss.
Pregnancy and fibroids
Fibroids usually don’t interfere with conception and pregnancy. However, it’s possible that fibroids could cause infertility or pregnancy loss. Submucosal fibroids may prevent implantation and growth of an embryo. In such cases, doctors often recommend removing these fibroids before attempting pregnancy or if you’ve had multiple miscarriages. Rarely, fibroids can distort or block your fallopian tubes, or interfere with the passage of sperm from your cervix to your fallopian tubes.
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.