Uterine fibroids are noncancerous growths made of smooth muscle that develop in or on the uterus. They are extremely common: by age 50, roughly 70% of white women and 80% of Black women will have them, though many never know because fibroids often cause no symptoms at all. They range from too small to see with the naked eye to large enough to fill the pelvis, and they can appear alone or in clusters.
What Fibroids Are Made Of
A fibroid is a mass of smooth muscle cells packed tightly together in a whorling pattern, surrounded by a thick network of connective tissue called the extracellular matrix. That connective tissue scaffold is a big part of what gives fibroids their firm, rubbery texture. Despite the word “tumor,” fibroids are benign. They virtually never become cancerous.
Where They Grow
Fibroids are classified by their location in the uterus, and that location largely determines which symptoms they cause.
- Intramural fibroids grow within the muscular wall of the uterus. They’re the most common type and can stretch the uterus as they enlarge.
- Submucosal fibroids grow inward, bulging into the open cavity of the uterus. Even small submucosal fibroids tend to cause heavy bleeding because they press against the uterine lining.
- Subserosal fibroids grow outward from the uterus surface. They’re more likely to cause pressure symptoms, like a sense of fullness in the pelvis or pressure on the bladder.
- Pedunculated fibroids are submucosal or subserosal fibroids that hang from a stalk, either inside or outside the uterus.
Why They Develop
Fibroids are driven by reproductive hormones. Estrogen was long considered the primary fuel, but more recent research shows that progesterone plays an equally significant role. Fibroid tissue has higher concentrations of progesterone receptors than normal uterine muscle, which makes it more responsive to progesterone’s growth signals. Progesterone also promotes the buildup of connective tissue within fibroids and encourages the formation of new blood vessels that feed them.
This hormonal dependence explains two consistent patterns. First, fibroids almost always develop during the reproductive years, when estrogen and progesterone levels are high. Second, they typically shrink after menopause, when those hormone levels drop.
Black women are nearly five times more likely to develop fibroids than white women, and they tend to develop them at younger ages and with larger sizes. The reasons are not fully understood but likely involve a combination of genetic, hormonal, and environmental factors.
Common Symptoms
Many fibroids are discovered incidentally during a routine pelvic exam or imaging for something else entirely. When they do cause symptoms, the most common include:
- Heavy menstrual bleeding, sometimes severe enough to cause anemia
- Periods that last longer than a week or come more frequently
- Pelvic pressure or pain, sometimes described as a constant heaviness
- Frequent urination, from fibroids pressing on the bladder
- Constipation, if fibroids press against the rectum
- A visibly enlarged abdomen, in cases where fibroids grow large enough to make someone look pregnant
Some fibroids stay the size of a seed for years. Others grow to the size of a grapefruit or larger. Size alone doesn’t always predict symptoms. A small submucosal fibroid can cause heavier bleeding than a large subserosal one that sits quietly on the outer wall.
How Fibroids Affect Fertility and Pregnancy
Not all fibroids interfere with reproduction, but those that distort the shape of the uterine cavity can create real problems. They may physically block sperm from reaching the egg, prevent an embryo from traveling into the uterus, or compress the uterine lining in ways that make implantation less likely. Women with cavity-distorting fibroids have significantly lower implantation rates, lower clinical pregnancy rates, and higher miscarriage rates.
During pregnancy, fibroids are associated with a range of complications: early pregnancy loss, preterm labor, abnormal placenta positioning, restricted fetal growth, and higher rates of cesarean delivery. Some fibroids grow rapidly during pregnancy due to the surge in hormones, and the resulting pain from stretching or loss of blood supply to the fibroid can be significant. None of this means pregnancy with fibroids is impossible. Many women carry pregnancies to term without incident. But fibroids that push into the uterine cavity deserve evaluation if you’re trying to conceive or are already pregnant.
How They’re Diagnosed
Ultrasound is the first-line tool. A technician may scan across your abdomen or use a vaginal probe (transvaginal ultrasound) to map the number, size, and location of fibroids. This is usually enough for a straightforward diagnosis.
MRI provides more detail when the picture is complex. It can distinguish fibroids from other types of growths, precisely map their positions, and help plan treatment. It’s especially useful when the uterus is very large or when someone is approaching menopause, since fibroids can mimic other conditions in that age group.
If your doctor needs a closer look at the inside of the uterus, particularly to evaluate submucosal fibroids, they may recommend hysterosonography (where sterile saline is used to expand the uterine cavity during ultrasound) or hysteroscopy (where a thin, lighted scope is inserted through the cervix for a direct view).
Treatment Options
If fibroids aren’t causing symptoms, treatment is usually unnecessary. Monitoring with periodic imaging is often all that’s needed. When symptoms become disruptive, treatment typically starts with medication before moving to procedures.
Medication
Medical management is recommended as the first step in most cases. Hormonal treatments can reduce bleeding and slow fibroid growth, though they don’t eliminate fibroids permanently. The goal is symptom relief, and for many women, medication provides enough control to avoid surgery.
Non-Surgical Procedures
Uterine fibroid embolization (UFE) works by cutting off a fibroid’s blood supply. A specialist threads a thin catheter into the arteries that feed the fibroids and injects tiny particles that block blood flow. Starved of nutrients, the fibroids shrink. Nearly 90% of patients experience symptom relief, and most return to normal activities within one to two weeks.
MRI-guided focused ultrasound (MRgFUS) uses concentrated sound waves to heat and destroy fibroid tissue while MRI ensures precision. Recovery is fast, typically a day or two, and most patients see significant symptom improvement within six months, with relief lasting at least three years.
Surgery
Myomectomy removes the fibroids while preserving the uterus. It’s the preferred surgical option for anyone who wants to keep the possibility of future pregnancy. Laparoscopic or robotic-assisted myomectomy is typically an outpatient procedure with a two-to-three-week recovery. Abdominal myomectomy, used when fibroids are very large or numerous, requires a one-to-two-day hospital stay and four to six weeks of recovery.
For submucosal fibroids smaller than 5 centimeters that hang into the uterine cavity, hysteroscopic myomectomy is the procedure of choice. The surgeon works through the cervix with no abdominal incisions at all.
Hysterectomy, the complete removal of the uterus, is the only treatment that guarantees fibroids won’t return. Current guidelines recommend it primarily for postmenopausal patients with persistent symptoms or when other treatments have failed. For women still in their reproductive years, alternatives to hysterectomy are considered first-line.
Which Treatment Fits Which Situation
The best approach depends on three factors: how severe your symptoms are, where exactly the fibroids sit, and whether you want to become pregnant. If you’re hoping to conceive and fibroids are distorting your uterine cavity, surgical removal of the fibroids is generally recommended. If fertility isn’t a concern and bleeding is the main issue, medication, embolization, or focused ultrasound may be enough. When fibroids coexist with another condition called adenomyosis (where tissue similar to the uterine lining grows into the uterine wall), treatment choices narrow somewhat, with medication and embolization being the usual starting points.
Fibroids can recur after any treatment that leaves the uterus in place. Myomectomy, embolization, and focused ultrasound all carry some chance of new fibroids developing over time. This doesn’t mean those treatments aren’t worthwhile. It just means follow-up imaging is part of the long-term plan.