Myomas are noncancerous growths that develop in or on the uterus. You’ll also hear them called fibroids or, in medical terms, uterine leiomyomas. They are the most common pelvic tumors in women, and ultrasound studies show they can be identified in 69% to 83% of women by age 50. More than half of those women have no symptoms at all.
What Myomas Are Made Of
A myoma is a mass of smooth muscle cells and connective tissue that grows in or around the uterine wall. They can be as small as a seed or large enough to distort the shape of the uterus. Some women develop a single myoma; others have several at once. Despite being classified as tumors, they are almost always benign. A meta-analysis of surgeries performed on presumed fibroids found that the chance of a myoma actually being cancerous (a leiomyosarcoma) was roughly 1 in 2,000. When only the most rigorous prospective studies were included, that estimate dropped to about 1 in 8,300.
Where They Grow
Myomas are categorized by their location in the uterine wall, and location matters because it determines which symptoms you experience and which treatments work best. The international classification system used by gynecologists recognizes several types based on where the growth sits relative to the inner lining, the muscle wall, and the outer surface of the uterus.
- Submucosal myomas grow into or just beneath the inner lining of the uterus. These are most likely to cause heavy bleeding and fertility problems because they can distort the space where an embryo would implant.
- Intramural myomas sit entirely within the muscular wall. They’re the most common type and can enlarge the uterus as they grow.
- Subserosal myomas develop on or near the outer surface of the uterus. They tend to cause pressure symptoms rather than bleeding.
- Pedunculated myomas are attached to the uterus by a stalk, either on the outer surface or dangling into the uterine cavity.
A single myoma can span multiple layers. A growth that started near the inner lining but extends toward the outer surface might be classified across more than one category.
Who Gets Them
Most women will develop at least one myoma during their lifetime, but the timing and severity vary significantly by ethnicity. Women of African ancestry tend to develop myomas 10 to 15 years earlier and more often have larger growths of greater volume. The incidence among Black women is roughly three times higher than among white, Asian, or Hispanic women. More recent data also suggest that women from East, South, and Southeast Asian backgrounds have higher diagnosis rates than previously recognized.
Why They Grow
Myomas are hormone-driven. Both estrogen and progesterone fuel their growth by activating signaling pathways that trigger cell multiplication. Estrogen, in particular, stimulates the release of growth factors that act as chemical signals telling myoma cells to keep dividing. Progesterone plays a more complex role, sometimes promoting growth and sometimes inhibiting it, but evidence shows it can directly increase cell proliferation in myoma tissue.
This hormonal dependence is why myomas typically develop during the reproductive years when estrogen and progesterone levels are highest, and why they commonly shrink after menopause when those hormone levels drop. It also explains why pregnancy, with its surge of hormones, can sometimes cause existing myomas to grow rapidly.
Common Symptoms
Whether a myoma causes problems depends on its size, number, and location. When symptoms do occur, they commonly include:
- Heavy or prolonged periods, sometimes severe enough to cause anemia from ongoing blood loss
- Bleeding between periods
- Pelvic pressure or fullness in the lower abdomen, especially as myomas grow larger
- Frequent urination, caused by a myoma pressing on the bladder
- Pain in the belly, lower back, or during sex
Submucosal myomas, even small ones, tend to cause the most noticeable bleeding because of their position against the uterine lining. Large subserosal or intramural myomas are more likely to produce that sensation of heaviness or pressure, and they can press on nearby organs like the bladder or bowel.
Myomas and Fertility
Not all myomas affect the ability to conceive, but submucosal myomas are a concern. Because they grow into or distort the uterine cavity, they can interfere with embryo implantation and early development. The American Society for Reproductive Medicine notes that removing submucosal myomas in women trying to conceive is generally recommended, even when those myomas aren’t causing other symptoms. Intramural and subserosal myomas have a less clear impact on fertility, and the decision to remove them before conception is more case-by-case.
Medication Options
Medications for myomas focus on controlling symptoms, particularly heavy bleeding, rather than eliminating the growths entirely. The most targeted options are oral drugs that work by suppressing the hormonal signals driving myoma growth. Two are currently FDA-approved in the U.S. for treating heavy bleeding caused by fibroids: elagolix (sold as Oriahnn) and relugolix (sold as Myfembree). Both are taken daily and combine a hormone-blocking ingredient with low-dose hormones to prevent the bone loss and hot flashes that come with full hormone suppression. Treatment courses are typically limited to 24 months.
These medications can significantly reduce menstrual bleeding, but myomas generally return to their previous size after the medication is stopped. For many women, they serve as a bridge, either to manage symptoms while approaching menopause or to prepare for a procedure.
Procedural Treatments
When symptoms are severe or fertility is a concern, procedural options become more relevant. The two most common are myomectomy and uterine artery embolization (UAE).
Myomectomy is surgery to remove the myomas while leaving the uterus intact. It can be done through a small incision, through the vagina (for submucosal myomas), or through a larger abdominal incision for bigger or more numerous growths. It’s generally preferred for women who want to preserve fertility. A large meta-analysis of nearly 200,000 patients found that myomectomy has a significantly lower rate of needing a repeat procedure compared to UAE, with roughly half the re-intervention risk.
Uterine artery embolization takes a different approach. A specialist threads a thin catheter into the blood vessels feeding the myomas and injects tiny particles that block blood flow, causing the growths to shrink. UAE typically means a shorter hospital stay and faster initial recovery than myomectomy, though the difference in hospital duration wasn’t statistically significant across all studies. The trade-off is a higher likelihood of needing additional treatment down the line.
A newer, completely noninvasive option is high-intensity focused ultrasound (HIFU), which uses targeted sound waves guided by MRI to heat and destroy myoma tissue without any incision. Studies show it reduces bulk-related and menstrual symptoms in about 51% of patients after six months, and shrinks treated myomas by roughly 30% over three to six months. It isn’t suitable for every myoma, particularly those close to the bowel or ones that can’t be clearly visualized on imaging.
Hysterectomy, the complete removal of the uterus, remains the only treatment that guarantees myomas won’t return. It’s typically reserved for women with severe symptoms who are done having children.