Merck Manual

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Uterine Fibroids

(Leiomyomas; Myomas)


David G. Mutch

, MD, Washington University School of Medicine;

Scott W. Biest

, MD, Washington University School of Medicine

Reviewed/Revised May 2023
Topic Resources

A fibroid is a noncancerous tumor of the uterus that is composed of muscle and fibrous tissue.

  • Uterine fibroids are very common, occurring in approximately 70% of White women and 80% of Black women in the United States.

  • Fibroids may cause no symptoms or can cause abnormal uterine bleeding or pressure or pain in the pelvis, and sometimes constipation, an urge to urinate frequently, infertility, or pregnancy complications.

  • Doctors do a pelvic examination and usually ultrasonography to confirm the diagnosis.

  • Treatment is necessary only if fibroids cause problems.

  • Doctors may prescribe medications to control the symptoms, but surgery or a procedure to destroy or remove the fibroids is often needed to relieve symptoms or to improve fertility.

Fibroids are also called leiomyomas or myomas.

The Uterus, Cervix, and Cervical Canal

Fibroids in the uterus are the most common noncancerous tumor (mass) of the female reproductive tract. By age 45, about 70% of women develop at least one fibroid. Many fibroids are small and cause no symptoms. But about one half of Black women and one fourth of White women eventually develop fibroids that cause symptoms.

Did You Know...

  • By age 45, about 7 out of 10 women develop fibroids of the uterus.

The cause of fibroids is unknown. High levels of estrogen and possibly progesterone (female hormones) seem to stimulate their growth. Fibroids may become larger during pregnancy (when levels of these hormones increase), and fibroids tend to shrink after menopause (when levels decrease drastically).

Fibroids may be microscopic or as large as a basketball. Many women have more than one fibroid. Sometimes, if fibroids grow too large, they may not be able to get enough blood. As a result, they begin to degenerate (tissue starts to die without enough blood supply), and this causes pain.

Fibroids may grow in different parts of the uterus, usually in the wall (which has three layers):

  • Under the outer surface of the uterus (subserosal fibroids)

  • In the wall of the uterus (intramural fibroids)

  • Under the inside layer (lining or endometrium) of the uterus (submucosal fibroids)

Sometimes fibroids grow in other locations, such as the cervix (bottom part of the uterus) or the broad ligament (connective tissue that surrounds the uterus).

Fibroids may be contained completely within the wall of the uterus, or they may protrude into other areas of the body. Fibroids can vary in shape. Some fibroids grow from a stalk (called pedunculated fibroids) and can protrude into the abdominal cavity, which can cause pressure on surrounding organs, such as the intestines or bladder. Some fibroids extend into the interior of the uterus (called intracavitary fibroids).

Some cancerous tumors of the uterus look similar to fibroids on imaging studies and may cause similar symptoms, such as abnormal bleeding. These cancerous tumors are rare, occurring in fewer than 1% of women with uterine masses that look similar to fibroids. Doctors do further evaluation if cancer is suspected. Based on current research, it is not thought that the typical type of fibroid changes and develops into cancer.

Where Uterine Fibroids Grow

Fibroids can grow in different parts of the uterus:

  • Under the outer surface of the uterus (subserosal fibroids)

  • In the wall of the uterus (intramural fibroid)

  • Under the lining of the uterus (submucosal fibroid)

Some fibroids grow on a stalk and can protrude into the abdomen or the uterine cavity. They are called pedunculated fibroids.

Where Uterine Fibroids Grow

Symptoms of Fibroids

Symptoms depend on

  • Location in the uterus

  • Size

  • Number of fibroids

Many fibroids do not cause symptoms. The larger the fibroid, the more likely it is to cause symptoms.

A common symptom of fibroids is abnormal uterine bleeding. This can be heavy menstrual periods or periods that last longer than usual (more than 8 days in a cycle). Sometimes fibroids cause bleeding between periods. Bleeding may be severe and can result in anemia Overview of Anemia Anemia is a condition in which the number of red blood cells is low. Red blood cells contain hemoglobin, a protein that enables them to carry oxygen from the lungs and deliver it to all parts... read more .

Fibroids in the wall of the uterus (intramural) may cause heavy bleeding by making it difficult for the uterus to contract. Contracting is how the uterus controls blood flow during a menstrual period or other episodes of uterine bleeding.

Fibroids located under the lining of the uterine cavity (submucosal) cause bleeding by changing the surface of the uterine cavity and the lining, which is shed during a menstrual period. Fibroids that protrude into the cavity of the uterus (intracavitary) cause the most change in the surface and usually cause more severe abnormal bleeding. Changes in the uterine cavity may also cause infertility Overview of Infertility Infertility is a disease defined by the inability to achieve a pregnancy and/or the need for medical intervention to achieve a successful pregnancy. Infertility is defined as disease by the... read more Overview of Infertility by blocking the fallopian tubes or making it difficult for a pregnancy to implant, which can interfere with getting pregnant or increase the risk of miscarriage Miscarriage A miscarriage is a pregnancy loss before 20 weeks of pregnancy. Miscarriages are very common, especially early in pregnancy. Most of the time, the cause of a miscarriage is unknown, but it may... read more .

Large fibroids may cause pain, pressure, or a feeling of heaviness in the pelvic area during or between menstrual periods. This may be because the fibroids make the uterus larger overall, causing the abdomen to distend (stick out), or the uterus may press on surrounding organs, such as the intestines or bladder. Pedunculated fibroids that protrude into the abdomen can also press on surrounding organs and tissues and cause pressure or pain. Fibroids may press on the bladder, making a woman need to urinate more frequently or more urgently. Sometimes they press on other parts of the urinary tract and can block the flow of urine. They may press on the rectum, causing discomfort and constipation.

A fibroid growing on a stalk may twist, cutting off its blood supply, and cause severe pain.

Fibroids that are growing or degenerating can cause pressure or pain. Pain due to degenerating fibroids can last as long as they continue to degenerate.

Fibroids that cause no symptoms before pregnancy may cause problems during pregnancy. Problems include

Diagnosis of Fibroids

  • Imaging, usually ultrasonography

Doctors may suspect fibroids based on symptoms or results of a pelvic examination. However, imaging tests are often needed to confirm the diagnosis of uterine fibroids.

Imaging tests include

Occasionally, those test results are unclear, and magnetic resonance imaging (MRI) is done.

If women have had abnormal bleeding, such as very heavy or prolonged menstrual periods or bleeding between periods, doctors may want to exclude cancer of the uterus Cancer of the Uterus The most common type of cancer of the uterus develops in the lining of the uterus (endometrium) and is called endometrial cancer. Endometrial cancer usually affects women after menopause. It... read more Cancer of the Uterus . So they may do the following:

For hysteroscopy, a viewing tube is inserted through the vagina and cervix into the uterus. A local, regional, or general anesthetic is often used for patients undergoing a D & C or hysteroscopy.

Treatment of Fibroids

  • Medications to relieve symptoms or shrink fibroids

  • Sometimes surgery to remove the entire uterus or only the fibroids

  • Sometimes procedures to destroy the fibroids

For most women who have fibroids but no bothersome symptoms or other problems, treatment is not required. They are reexamined every 6 to 12 months so that doctors can determine whether symptoms are worsening or lessening and whether fibroids are growing. Such periodic monitoring is sometimes called watchful waiting.

Several treatment options, including medications and surgery, are available if bleeding or other symptoms worsen or if fibroids enlarge substantially.

Medications to treat fibroids

A few medications may be used to relieve symptoms or to shrink fibroids, but their effects are only temporary. No medication can treat fibroids so that they permanently resolve.

Medications used to treat fibroids may be hormonal or nonhormonal.

The first medications given are usually those that decrease bleeding, are easy to use, and are well-tolerated, including

  • Estrogen-progestin contraceptives

  • Progestins (for example, a levonorgestrel-releasing intrauterine device [IUD])

  • Tranexamic acid

  • Nonsteroidal anti-inflammatory drugs (NSAIDs)

Progestins Hormone Therapy for Menopause Menopause is the permanent end of menstrual periods, ovulation, and fertility. For up to several years before and just after menopause, estrogen levels fluctuate widely, periods become irregular... read more Hormone Therapy for Menopause given alone without estrogen (such as medroxyprogesterone acetate or megestrol) can control bleeding in some women, but these medications may not shrink fibroids as much as GnRH analogs Medications to treat fibroids Medications to treat fibroids . They reduce bleeding by preventing the lining of the uterus from growing too much. When the uterine lining grows too much, there is more of it to break down and be shed during menstruation. As a result, menstrual bleeding may be heavier than usual. Progestins are taken by mouth. They may be taken every day or only for 10 to 14 consecutive days each menstrual cycle. Or doctors may give women injections of medroxyprogesterone acetate every 3 months or insert an intrauterine device (IUD Intrauterine Devices (IUDs) Intrauterine devices (IUDs) are small, flexible, T-shaped plastic devices that are inserted into the uterus. In the United States, 12% of women who use contraception use IUDs. IUDs are popular... read more Intrauterine Devices (IUDs) ) that releases a progestin called levonorgestrel. Estrogen-progestin contraceptives and levonorgestrel-releasing IUDs are good options for women who also want contraception. However, these medications may have bothersome side effects, such as weight gain, depression, and irregular bleeding.

Tranexamic acid works by preventing blood clots (which are made by the body to help stop bleeding) from breaking down as quickly. As a result, bleeding decreases.

Nonsteroidal anti-inflammatory drugs (NSAIDs) may relieve pain but may not reduce bleeding.

Other medications that are sometimes used to treat symptomatic fibroids include

  • Gonadotropin-releasing hormone (GnRH) analogs

  • Antiprogestins

  • Selective estrogen receptor modulators (SERMs)

  • Danazol

Gonadotropin-releasing hormone (GnRH) analogs are used if other medications have not been effective, bleeding is persistent, and the woman has anemia Overview of Anemia Anemia is a condition in which the number of red blood cells is low. Red blood cells contain hemoglobin, a protein that enables them to carry oxygen from the lungs and deliver it to all parts... read more (too few red blood cells in the blood). GnRH analogs are either agonists (such as leuprolide) or antagonists (such as elagolix and relugolix). Both types of analogs can shrink fibroids and reduce bleeding by creating a temporary state that is similar to menopause, which causes the body to produce less estrogen and progesterone. Because they shrink the fibroids and reduce bleeding, doctors may give GnRH analogs before surgery to make removal of fibroids easier, reduce blood loss, and thus reduce the risks of surgery.

The medications may be taken as a pill, injected, or implanted as a pellet under the skin. Nafarelin, another GnRH agonist, can be used as a nasal spray.

GnRH agonists are usually taken for less than 6 months. If taken for a long time, they may reduce bone density and increase the risk of osteoporosis Osteoporosis Osteoporosis is a condition in which a decrease in the density of bones weakens the bones, making breaks (fractures) likely. Aging, estrogen deficiency, low vitamin D or calcium intake, and... read more Osteoporosis . Low doses of estrogen, usually combined with a progestin (a medication that is similar to the hormone progesterone), may be given with GnRH agonists to help prevent loss of bone density.

Within 6 months after GnRH agonists are stopped, fibroids may become as large as they were before treatment.

Antiprogestins, such as mifepristone and related medications, inhibit the activity of the hormone progesterone. As a result, the uterus and fibroids shrink.

Selective estrogen receptor modulators (SERMs), such as raloxifene and related medications, reverse some of estrogen’s effects. They may not be as effective as other medications.

Danazol (a synthetic hormone related to testosterone) inhibits the activity of estrogen and progesterone. It is rarely used and has many side effects, such as weight gain, acne, increased body hair (hirsutism), swollen ankles, loss of scalp hair, vaginal dryness, and lowering of the voice.

Procedures to treat fibroids

Several minimally invasive procedures are available to treat fibroids. These are usually used if medications are not effective and a woman does not want surgery or has health reasons why she should not have surgery.

After having one of these procedures, women should not become pregnant. Whether pregnancy after these procedures is safe is unclear.

For uterine artery embolization, doctors use an anesthetic to numb a small area of the thigh and make a small puncture hole or incision there. Then, they insert a thin, flexible tube (catheter) through the incision into the main artery of the thigh (femoral artery). The catheter is threaded to the arteries that supply blood to the fibroid, and small synthetic particles are injected. The particles travel to the small arteries supplying the fibroid and block them. As a result, the fibroid dies, then shrinks. Most of the rest of the uterus appears to be unaffected. However, whether the fibroid will regrow (because blocked arteries reopen or new arteries form) is unknown.

After uterine artery embolization, most women have pain and cramping in the pelvis, nausea, vomiting, fever, fatigue, and muscle aches. These symptoms develop within 48 hours after the procedure and gradually lessen over 7 days. An infection may develop in the uterus or surrounding tissues. Women recover more quickly after this procedure than after a hysterectomy or myomectomy, but they tend to have more complications and more return visits to the doctor. If fibroids continue to be a problem or grow back after embolization, hysterectomy is recommended.

Magnetic resonance-guided focused ultrasound surgery uses sound waves to destroy fibroids.

Surgery for fibroids

Surgery is usually considered for women who have any of the following:

  • Fibroids that are rapidly enlarging

  • Bleeding that continues or recurs despite treatment with medications or minimally invasive procedures

  • Severe or persistent pain

  • Large fibroids that cause problems, such as the need to urinate frequently, constipation, pain during sexual intercourse, or blockage of the urinary tract

  • For women who want to conceive, fibroids that have caused infertility or repeated miscarriages

Several types of surgery can be done. The recommended surgery depends on the size, number, and location of fibroids. However, before making a decision about treatment, women should talk to their doctor about the problems that can result from each type of surgery so that they can make an informed decision.

Surgery to remove fibroids traditionally involves one of the following:

For hysterectomy, surgeons may use one of the following methods:

Laparoscopic surgery can be done with robotic assistance. The robot is a device used to control and manipulate surgical instruments inserted with the laparoscope. The laparoscope sends a three-dimensional image of the body's interior to a console. Surgeons sit at a console to view this image, and a computer translates their hand movements into precise movements of the surgical instruments.

For myomectomy, surgeons may use

  • Hysteroscopy: Surgeons insert a telescope-like lighted device (hysteroscope) through the vagina into the uterus. Using instruments inserted through this tube, surgeons can cut tissue and remove fibroids on the inside of the uterus.

  • Laparoscopy

  • Laparotomy

Laparoscopy and hysteroscopy are outpatient procedures, and recovery is faster than recovery after laparotomy. However, sometimes removing fibroids using laparoscopy or hysteroscopy may be difficult or impossible—for example, when there are many fibroids, when they are very large, or when they are embedded deeply in the wall of the uterus. In such cases, doctors do a laparotomy.

Hysterectomy may be preferred to myomectomy or may be required for several reasons:

A procedure called morcellation may be done during myomectomy or hysterectomy. For this procedure, surgeons cut the fibroids or uterine tissue into small pieces so that the pieces can be removed through a smaller incision. Rarely, women with fibroids have cancer of the uterus Cancer of the Uterus The most common type of cancer of the uterus develops in the lining of the uterus (endometrium) and is called endometrial cancer. Endometrial cancer usually affects women after menopause. It... read more Cancer of the Uterus that is unsuspected and undiagnosed. If morcellation is done in such women, the cancer cells may be spread into the abdomen and pelvis. In such cases, cancer can develop in other locations. Doctors can use surgical techniques to prevent tissue from being spread, such as using a bag to catch all of the pieces of the fibroid and remove them from the body. Before surgery for fibroids, women should evaluated for uterine cancer if they have any concerning symptoms and they should be informed of the very small risk of spreading cancerous cells if morcellation is done.

Radiofrequency fibroid ablation can be used during hysteroscopy or laparoscopy to destroy, rather than remove, fibroids. Doctors insert a needle that transmits an electrical current or heat into the fibroid to destroy its core. After these treatments, fibroids may grow back. In such cases, another treatment or a hysterectomy may be recommended.

Choice of treatment for fibroids

Choice of treatment for fibroids depends on the woman's situation, but women and their doctors may discuss the choice based on the following general guidelines:

  • If the fibroids do not cause any symptoms: No treatment but continue to follow up with a doctor.

  • If a woman is going through or has passed through menopause: Undergo evaluation for uterine cancer if there is abnormal uterine bleeding and, if results are normal, continue to follow up with a doctor to see if symptoms resolve, which usually happens as fibroids decrease in size after menopause.

  • If fibroids cause symptoms: Start with medications for most women, unless surgery is likely to be much more effective (such as for fibroids that are very large or for intracavitary submucosal fibroids). If medications are not effective, doctors treat with a minimally invasive procedure or surgery.

  • If fibroids cause infertility: Undergo myomectomy to remove fibroids.

  • If symptoms are severe and other treatments are ineffective, particularly if a woman does not want to become pregnant: Have a hysterectomy, possibly preceded by treatment with medications.

Drugs Mentioned In This Article

Generic Name Select Brand Names
AfterPill, EContra EZ, EContra One-Step, Fallback Solo, Kyleena , LILETTA, Mirena, My Choice, My Way, Next Choice, Next Choice One Dose, Norplant, Opcicon One-Step, Plan B, Plan B One-Step , Preventeza, React, Skyla, Take Action
Cyklokapron, Lysteda
Amen, Depo-Provera, Depo-subQ Provera 104, Provera
Megace, Megace ES
CAMCEVI, Eligard, Fensolvi, Lupron, Lupron Depot, Lupron Depot-Ped, Viadur
Korlym, Mifeprex
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