Understanding Uterine Fibroids

by National Institute of Health

Uterine fibroids are the most common, non-cancerous tumors in women of childbearing age. They are the cause of more than 200,000 hysterectomies every year. They have no known cause and only a few treatment options. Uterine fibroids not only affect the women who have them, but they also impact the partners, spouses, and families of these women, sometimes to a great degree. Despite the fact that they may affect one- quarter of all the women in the United States, fibroids continue to baffle health care providers and scientists.

What are uterine fibroids?

Uterine fibroids are tumors or lumps made of muscle cells and other tissue that grow within the wall of the uterus. Fibroids may grow as a single tumor or in clusters. A single fibroid can be less than one inch in size or can grow to eight inches across or more. A bunch or cluster of fibroids can also vary in size.

Where do uterine fibroids grow?

Most fibroids grow within the wall of the uterus. Health care providers put fibroids into three groups based on where they grow:

Submucosal fibroids grow just underneath the uterine lining.

Intramural fibroids grow in between the muscles of the uterus.

Subserosal fibroids grow on the outside of the uterus.

Some fibroids grow on stalks that grow out from the surface of the uterus, or into the cavity of the uterus. These are called pedunculated fibroids.

What are the symptoms of uterine fibroids?

Many women don't feel any symptoms with uterine fibroids. But fibroids can cause the following symptoms:

• Heavy bleeding or painful periods
• Bleeding between periods
• Feeling "full" in the lower abdomen - sometimes called "pelvic pressure"
• Urinating often (results from a fibroid pressing on the bladder)
• Pain during sex
• Lower back pain
• Reproductive problems, such as infertility, multiple miscarriages, and early onset of labor during pregnancy

What causes uterine fibroids?

Currently, we know little about what causes uterine fibroids. Scientists have a number of theories, but none of these ideas explains fibroids completely. Most likely, fibroids are the end result of many factors interacting with each other. These factors could be genetic, hormonal, environmental, or a combination of all three. Once we know the cause or causes of fibroids, our efforts to find a cure or even prevent fibroids will move ahead more quickly.

Who gets uterine fibroids?

Most of the time, fibroids grow in women of childbearing age. Research studies estimate that health care providers diagnose up to 30 percent of women of childbearing age with uterine fibroids; but, because some women show no symptoms of fibroids, as many as 77 percent of women of childbearing age could have the condition, without knowing it. We don't know exactly how many new cases of fibroids occur in a year, nor do we know how many women have fibroids at any one time.

There have also been reports of rare cases in which young girls who have not yet started their periods (pre-pubertal) had small fibroids. Researchers have also found that fibroids sometimes run in families. Researchers now recognize several risk factors for uterine fibroids.

Current statistics place African American women at three- to five-times greater risk than white women for fibroids. Women who are overweight or obese for their height (based on body mass index or BMI*) are also at slightly higher risk for fibroids than women who are average weight for their height. Women who have given birth appear to be at lower risk for uterine fibroids. But, because we don't know what causes fibroids, we also don't know what increases or decreases the risk.

Does having uterine fibroids mean that I will be infertile or unable to have children?

Most women who have fibroids do not have problems with fertility and are able to get pregnant. In some cases, fibroids can prevent a woman from getting pregnant through natural methods. However, advances in treatments for fibroids and infertility have greatly improved the chances for a woman to get pregnant, even if she has uterine fibroids.

Researchers are still looking into what role, if any, uterine fibroids play in infertility. Currently, though, there are few answers. One study's results suggest that only submucosal fibroids have a negative impact on fertility, but these results are not yet confirmed. The relationship between fibroids and infertility remains a very active research area.

Does having uterine fibroids mean I will need a hysterectomy?

Hysterectomy (removal of the uterus) is not the best option for every woman with uterine fibroids. If you want to have children, then you would want to avoid this treatment. Likewise, if you don't have symptoms of uterine fibroids, or your fibroids are small, you may have better results from pain medications or hormone treatments. Health care providers are also exploring less-invasive surgical treatments for fibroids that save the uterus.

In some cases, though, a hysterectomy is the best method of treatment. If you have uterine fibroids and are thinking about hysterectomy, make sure you talk over all features of the surgery with your doctor and your family. Having a hysterectomy means that you will no longer be able to have children. This process cannot be reversed, so be certain about your choice before having the surgery.

Keep in mind that the physical scars of the procedure may heal quickly, but some of the effects of hysterectomy are long-lasting. You may want to talk to women who have had the procedure before you decide to have your surgery. Many health care centers, women's clinics, and hospitals offer support groups for women who have had, or are in the process of having hysterectomies.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.