What Are Uterine Fibroids?

Quick Answer

Uterine fibroids are noncancerous growths of the muscle of the uterus. Most women have them by menopause, many never have symptoms, and they usually only need treatment when they cause heavy bleeding, pressure, pain or fertility problems.

Uterine fibroids are noncancerous growths that develop from the muscle tissue of the uterus. Doctors also call them leiomyomas or myomas. They are very common: ACOG estimates that up to 70% of women have them by menopause. Many fibroids cause no trouble at all. They matter when they cause symptoms such as heavy periods, pelvic pressure or pain, or when they affect your daily life or plans for pregnancy.

This guide explains what fibroids are, how common they are, who is more likely to get them, and how to tell whether yours need attention.

What fibroids are

A fibroid is a firm lump of muscle and connective tissue that grows in or on the wall of the uterus. The American College of Obstetricians and Gynecologists (ACOG) describes them as the most common type of growth found in a woman's pelvis. You can have a single fibroid or many of different sizes.

Fibroids vary widely in size. The federal Office on Women's Health (OWH) says they can be as small as an apple seed or as big as a grapefruit, and ACOG notes that some grow more than 5 to 6 inches wide. A fibroid may stay small for years and then grow quickly, or grow slowly over a long period.

Where a fibroid sits matters as much as its size. Some grow into the inside of the uterus, some stay within the muscle wall, and some bulge from the outer surface or hang from a stalk. Our guide to the types of uterine fibroids explains the classification doctors use and why location affects symptoms and treatment.

How common are fibroids?

Fibroids are among the most common conditions in women of reproductive age. The exact number depends on who is studied and whether women are screened with ultrasound or counted only after a diagnosis.

Source	What it found
Baird et al., 2003 (ultrasound screening of 1,364 randomly selected women aged 35 to 49)	Estimated chance of developing fibroids by age 50: more than 80% for Black women and nearly 70% for white women. About half of women with no prior diagnosis had fibroids on ultrasound.
Stewart et al., 2017 (systematic review of 60 publications)	Reported prevalence ranged from 4.5% to 68.6%, depending on the population and how fibroids were detected.
ACOG Practice Bulletin 228, 2021	Fibroids are estimated to occur in up to 70% of women by menopause, with about 25% significant enough to need treatment.
Office on Women's Health	About 20% to 80% of women develop fibroids by age 50.

The wide ranges are not a contradiction. Many fibroids are small and silent, so they are only found when someone looks for them with imaging. The Baird study found that about half of the women who had never been told they had fibroids actually did.

Who is more likely to have fibroids?

No one knows exactly what causes fibroids. The hormones estrogen and progesterone are involved in their growth, which is one reason they tend to shrink after menopause. ACOG's 2021 practice bulletin lists these factors as raising the risk:

Age, up until menopause
A family history of fibroids
A longer time since your last birth
High blood pressure
Obesity

Factors linked with a lower risk include having given birth more times, and use of oral hormonal contraceptives or the injectable contraceptive DMPA.

Race is one of the strongest associations. ACOG states that fibroids are 2 to 3 times more common in Black women than in white women, and that Black women tend to develop them at a younger age, are more likely to be anemic, and have larger uteri at diagnosis. ACOG's patient guidance notes these differences may be due to racism and inequities in society. You can read more in our article on fibroids in Black women.

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This article is part of our Fibroid Treatment Guide.

Do fibroids always cause symptoms?

No. Many women with fibroids never know they have them. They may be found by chance during a routine pelvic exam or an ultrasound done for another reason. ACOG's practice bulletin estimates that only about a quarter of fibroids are significant enough to require intervention, and a 2024 European gynecology society review put the share causing symptoms that warrant therapy at up to 50%.

When fibroids do cause problems, the most common are:

Heavy, long or more frequent periods, sometimes enough to cause anemia
Pelvic pressure, fullness or pain
Frequent urination or trouble emptying the bladder
Constipation or rectal pressure
Lower back pain or pain during sex
An enlarged abdomen

Our article on fibroid symptoms walks through each sign and explains what else can cause it.

Are fibroids dangerous?

Fibroids are benign. The Office on Women's Health describes them as almost always noncancerous and says having fibroids does not raise your risk of a cancerous growth in the uterus. A rare cancer called leiomyosarcoma can look like a fibroid, which is why doctors pay attention to a growth that enlarges quickly or appears after menopause. Our article Are fibroids cancer? covers this in more detail.

The more common risk from fibroids is ongoing blood loss. Heavy periods month after month can lower your iron and lead to anemia, which can leave you tired, short of breath or lightheaded.

When fibroids matter

Having fibroids is not, on its own, a reason for treatment. ACOG says fibroids that cause no symptoms, are small, or occur in a woman nearing menopause often do not need treatment. Fibroids usually shrink after menopause.

ACOG lists signs that may mean treatment is worth discussing:

Heavy or painful periods that cause anemia or disrupt your normal activities
Bleeding between periods
Uncertainty about whether a growth is a fibroid or another type of tumor
Rapid growth of a fibroid
Infertility
Pelvic pain

Infertility deserves a careful note. ACOG says fibroids may cause infertility, although other causes are more common and should be looked at first. Fibroids that bulge into the inside of the uterus are the type most often linked with fertility problems.

What are the treatment options?

If your fibroids bother you, you have more than one path. ACOG says the choice depends on your own wishes and on the size and location of the fibroids. Options include:

Watchful waiting for fibroids that cause no symptoms or only mild ones
Medication, such as hormonal IUDs, tranexamic acid or GnRH-antagonist combinations, which mainly reduce bleeding
Myomectomy, surgery that removes fibroids and keeps the uterus
Uterine fibroid embolization (UFE), a catheter procedure that blocks the blood supply to fibroids so they shrink, without removing the uterus
Radiofrequency ablation and focused ultrasound, which use energy to shrink fibroids
Hysterectomy, removal of the uterus, the definitive surgical option, after which pregnancy is no longer possible

Each option has trade-offs in recovery, the chance that more treatment is needed later, and what it means for future pregnancy. Our fibroid treatment guide compares them side by side. If you want to keep your uterus and avoid surgery, you can also read how uterine fibroid embolization (UFE) works, what the research shows, and who is a good candidate.

Next steps if you think you have fibroids

Fibroids are usually first suspected during a pelvic exam and confirmed with an ultrasound. Before your visit, it helps to note how long your periods last, how often you change pads or tampons, and any pressure, bladder or bowel symptoms. Bring a list of questions, such as how many fibroids you have, how big they are, where they are, and whether they have grown since any earlier scan.

If your fibroids are not causing problems, regular checkups may be all you need. If they are, you deserve a clear explanation of every reasonable option, not just one.

Frequently Asked Questions

Are uterine fibroids common?

Yes. In a 2003 ultrasound study of 1,364 women aged 35 to 49, the estimated chance of having fibroids by age 50 was more than 80% for Black women and nearly 70% for white women. Many of these fibroids caused no symptoms.

Are fibroids cancer?

No. Fibroids are benign growths. The Office on Women's Health says they are almost always noncancerous and that having fibroids does not raise your risk of a cancerous growth in the uterus.

Do all fibroids need treatment?

No. ACOG says fibroids that cause no symptoms, are small, or occur in a woman nearing menopause often do not need treatment. Treatment is worth discussing when they cause heavy bleeding, anemia, pain, pressure or fertility problems.

Do fibroids go away on their own?

Fibroids usually shrink after menopause, when hormone levels fall. Before menopause they may stay the same size, grow slowly, or grow quickly, so regular checkups help track them.

Can I keep my uterus if my fibroids need treatment?

Often, yes. Medication, myomectomy, uterine fibroid embolization and energy-based treatments all keep the uterus. Which one fits depends on your symptoms, your fibroids' size and location, and whether you want a future pregnancy.

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Sources

Medically reviewed by David Fox, MD, FACS, RPVI. This article is general information, not a substitute for a medical evaluation.

Living with heavy periods, pelvic pressure or other fibroid symptoms? Schedule a consultation with Dr. David Fox at Fox Vein & Vascular in Manhattan to find out whether uterine fibroid embolization is right for you. Call (212) 362-3470 or request a UFE consultation online.