A Beginner’s Guide to Uterine Fibroids

What Are Uterine Fibroids and Why Do They Develop?

Uterine fibroids, medically known as leiomyomas or myomas, are benign tumors made of smooth muscle cells and fibrous connective tissue that form in or on the muscular wall of the uterus, called the myometrium.^[2] Fibroids are almost never cancerous, and research shows that approximately 70% to 80% of women will develop at least one fibroid by the time they reach menopause, though many women have fibroids without ever developing noticeable symptoms.^[1]

How Do Fibroids Grow and Develop Over Time?

Fibroids develop when a single smooth muscle cell within the uterine wall begins dividing repeatedly, gradually forming a solid, rounded mass distinct from the surrounding uterine tissue.^[3] The rate at which a fibroid grows varies significantly from woman to woman, and even fibroid to fibroid within the same uterus: some fibroids remain stable in size for years without intervention, while others enlarge noticeably over just a few months, particularly during pregnancy or during any period of elevated estrogen exposure.

Because fibroid growth is hormonally driven, fibroids typically stop growing and often shrink somewhat once a woman reaches menopause and hormone production declines.

What Symptoms Do Fibroids Cause, and How Severe Can They Get?

Not every fibroid causes symptoms. In fact, research indicates that only about 25% to 30% of women with fibroids experience symptoms significant enough to require treatment.^[4] When fibroid symptoms do occur, the most common include heavy or prolonged menstrual bleeding, pelvic pressure or pain, frequent urination, constipation or bloating, and lower back pain.

Symptom severity is often tied more closely to a fibroid’s size, number, and specific location within the uterus than to the mere presence of a diagnosis. Persistent heavy menstrual bleeding from fibroids can also lead to iron-deficiency anemia over time, which is an important symptom to mention to your doctor even if it feels unrelated to your periods.

What Other Conditions Are Fibroids Commonly Confused With?

Because fibroid symptoms overlap with several other gynecologic conditions, an accurate diagnosis from a specialist matters more than guessing based on symptoms alone. Adenomyosis, a condition in which uterine lining tissue grows directly into the muscular uterine wall, can cause heavy bleeding and pelvic pain that closely resembles fibroid symptoms, yet adenomyosis is a distinct condition from fibroids with a different underlying cause.^[5]

Ovarian cysts and uterine polyps can also mimic fibroid symptoms such as pelvic pressure and abnormal bleeding, even though they form in entirely different tissue and typically require different diagnostic imaging and treatment approaches. A pelvic ultrasound or MRI is usually the most reliable way to distinguish fibroids from these look-alike conditions.

Are There Different Types of Uterine Fibroids Based on Location?

Fibroids are classified into distinct types based on exactly where they grow in relation to the uterine wall, and understanding fibroid type can help explain why two women with similarly sized fibroids may experience very different symptoms. Intramural fibroids grow within the muscular wall itself and are the most common fibroid type. Subserosal fibroids grow on the outer surface of the uterus and, because of their outward-facing position, can press on nearby organs like the bladder or bowel without necessarily affecting menstrual bleeding.^[7]

Submucosal fibroids grow just beneath the inner uterine lining, or endometrium, and are the fibroid type most likely to cause heavy or prolonged menstrual bleeding and fertility concerns. Pedunculated fibroids are a less common type that attach to the uterus by a thin stalk, giving them a mushroom-like appearance on imaging.

What Is a Fundal Fibroid and Where Does It Grow?

A fundal fibroid is simply a fibroid that develops at the fundus, the upper, dome-shaped portion of the uterus where the fallopian tubes connect.^[8] Fundal fibroids are not a separate structural category on their own; rather, they can be intramural, subserosal, or submucosal depending on how deep they grow within the uterine wall at that location. Because of their position at the top of the uterus, fundal fibroids can sometimes influence pregnancy-related monitoring, including fundal height measurements taken during prenatal visits.

Do Fibroids Only Grow in the Uterus, or Can They Spread Elsewhere?

Fibroids form specifically from uterine smooth muscle tissue, so by definition they only develop in or on the uterus itself and cannot spread to or originate in other organs.^[9] Growths found on the ovaries or elsewhere in the pelvis, such as ovarian cysts, are made of entirely different tissue and are not classified as fibroids, even though the pelvic pressure and bloating they cause can feel very similar.

This is one reason imaging that specifically visualizes the uterus, rather than relying on symptoms alone, is so important for an accurate diagnosis.

How Do Fibroids Develop, and Who Is Most at Risk for Fibroids?

The exact underlying cause of fibroids is not yet fully understood, but estrogen and progesterone are well established as key drivers of fibroid growth, which explains why fibroids typically develop during a woman’s reproductive years and often shrink once she reaches menopause and hormone production declines.^[10] Several risk factors are associated with a higher likelihood of developing fibroids, including having a family history of fibroids, obesity, vitamin D deficiency, and simply being within reproductive age.

Fibroids are also diagnosed significantly more often, and often at a younger age, in Black women compared with women of other racial backgrounds, with some research showing a prevalence as high as 80% in Black women by age 50 compared with 50% to 70% in white women.^[1] Researchers continue to study the genetic, environmental, and social factors that may contribute to this racial disparity in fibroid risk.

What Fibroid Treatment Options Are Available Today?

Watching and waiting can be a reasonable approach when fibroids are small and symptoms are mild or absent, but this strategy does not shrink existing fibroids and does not address bleeding, pressure, or pain that is already disrupting daily life.^[11]

For women whose fibroid symptoms are significant enough to interfere with work, sleep, or quality of life, minimally invasive, non-surgical fibroid treatment options exist that can relieve symptoms without requiring removal of the uterus.^[12]

Is UFE the Right Non-Surgical Treatment for My Fibroids?

Uterine Fibroid Embolization (UFE) is an outpatient, image-guided procedure that blocks the blood supply feeding uterine fibroids, causing the fibroids to gradually shrink over the following weeks and months. UFE preserves the uterus entirely and does not require the surgical incisions associated with a myomectomy or hysterectomy, making it a fertility-conscious option for many women who want to avoid major surgery.

Most patients who undergo UFE return to normal activities within one to two weeks, a much shorter recovery window than the four to six weeks typically associated with hospital-based surgical fibroid removal.

Unlike hysterectomy, which removes the uterus entirely, UFE does not remove any reproductive organs, and unlike myomectomy, UFE does not require an incision into the uterine wall itself, which can lower the risk of certain surgical complications.

It is important to understand that UFE treats the fibroids that already exist at the time of the procedure, but it does not prevent new fibroids from forming in the future, since new fibroids can still develop as long as a woman’s estrogen and progesterone levels continue to support fibroid growth.

Because UFE is performed on an outpatient basis with local anesthesia, many patients can be evaluated for candidacy and scheduled for treatment without an extended interruption to their work or family responsibilities.