Hearing that you have a growth in your uterus is understandably unsettling. Although uterine fibroids are usually benign, they can be problematic—causing pain or heavy menstrual bleeding, says the federal Office on Women's Health (OWH).
In the US, as many as 26 million people of childbearing age have uterine fibroids, says the US National Library of Medicine. More than half of these people experience symptoms.
What exactly are uterine fibroids, though, and what happens when you discover you have one? Here's what you need to know.
What are uterine fibroids?
Uterine fibroids are non-cancerous tumors, or masses, that grow in and around the muscle and connective tissue of the uterus, according to the Cleveland Clinic. They rare develop into cancer, and having uterine fibroids doesn't increase your risk of developing a uterine cancer, says OWH.
"Uterine fibroids develop from smooth muscle tissue in the uterus," says G. Thomas Ruiz, MD, ob-gyn lead at MemorialCare Orange Coast Medical Center in Fountain Valley, California. "Like any other tissue can, it starts cloning itself and growing on its own."
Dr. Ruiz says uterine fibroids are usually discussed in two contexts: size and location. The larger they are, the more likely they are to cause symptoms, he explains. (Alternatively, having several small fibroids that add up to the size of a larger growth can be problematic too.)
Fibroids can be as tiny as a seed or as massive as a watermelon, ranging from 1 millimeter to 20 centimeters (about 8 inches) or more in diameter, reports the Cleveland Clinic. At that point, it can cause weight gain, abdominal swelling, and pain, and large fibroids may also cause damage to the uterus or surrounding organs, interfere with pregnancy or fertility, and cause heavy bleeding, per UCLA Health.
As for location, OWH reports that fibroids grow in three different ways:
- From the wall of the uterus into the lining or cavity of the uterus. They're called submucosal fibroids.
- From the wall of the uterus outward, or outside the uterus, called subserosal fibroids.
- Only contained within the wall of the uterus, known as intramural fibroids.
Dr. Ruiz says submucosal fibroids usually present the earliest and may cause heavy bleeding, while intramural fibroids don't cause many issues unless they become very large. Subserosal fibroids are the least symptomatic and most common, he adds, but they can get big enough to outgrow their blood supply, which can cause severe pain because the tissue may die and become twisted, or infarcted.
What causes uterine fibroids?
There are no known causes of uterine fibroids, but Dr. Ruiz says there are some things that increase your chances of developing them.
"Family history [plays a part]," he says, "so if your mom had large uterine fibroids, you're predisposed to them as well."
In addition to genetics, age and race play a role; Black women have a much higher risk of developing fibroids, says Dr. Rose Chang-Jackson, ob-gyn at Austin Regional Clinic in Austin, Texas, as do older women with longer "reproductive lifespans."
Lastly, uterine fibroids often grow when estrogen levels are high, perhaps due to prolonged exposure to estrogen, per Johns Hopkins Medicine.
What are the symptoms of uterine fibroids?
The two primary symptoms of uterine fibroids are pain and bleeding, says Dr. Ruiz.
"[You may have] pelvic pain or pressure, pain during intercourse, and pain before or during menses," he explains, "and you may have heavier and longer periods or abnormal bleeding at abnormal intervals."
In other words, you might suspect you have uterine fibroids if your periods are unusually long and heavy or if you bleed unpredictably between periods.
But Dr. Ruiz also emphasizes that there's no universal experience of uterine fibroid symptoms, regardless of how large or small your fibroids are. He says that fairly large uterine fibroids can be found in a woman who is asymptomatic, while someone with only one small fibroid can experience clear symptoms.
How are uterine fibroids diagnosed?
Initially, says Dr. Chang-Jackson, most uterine fibroids are diagnosed from a physical exam.
"A patient will come into a well-woman visit for a pelvic exam, and we'll notice she has a large uterus," she explains, adding that a pelvic ultrasound is then typically recommended to confirm the diagnosis. An MRI may also be used, she says, especially if an exact location of the fibroid is needed for surgical planning.
According to the American College of Obstetrics and Gynecology, there are a few other tests which may be used to diagnose fibroids:
- Hysteroscopy, a scope that allows your doctor to see any fibroids within the uterus.
- Hysterosalpingography, an x-ray procedure using special dye to obtain images of the uterus and fallopian tubes.
- Laparoscopy, which involves a small incision, giving your doctor a good view of fibroids growing on the outside wall of the uterus.
How uterine fibroids are treated?
You may not need to treat your uterine fibroid at all; if you are asymptomatic and not planning a pregnancy, Lisa Hansard, MD, board-certified reproductive endocrinologist at Texas Fertility Center, says you may be able to sit back and let your body do the work for you.
"About 35% of women at age 35 have a uterine fibroid, but that doesn't mean you have to do anything about it," Dr. Hansard tells Health. "When women go through menopause, typically the fibroids stop growing or get smaller, so our goal is to get you to menopause without having to intervene—if we can do that, it's likely you won't need any treatment."
That said, if you are experiencing symptoms or have concerns about the location of your fibroid with regard to your fertility, you may need to undergo treatment. While fibroids may not affect a pregnancy at all, per Dr. Ruiz, their size and location can introduce complications to the pregnancy as well as to labor and delivery.
A 2017 study published in PLOS One, for example, assessed obstetric outcomes in women with and without uterine fibroids. Having uterine fibroids was associated with a higher risk of cesarean section as well as postpartum hemorrhage; it was also found that babies were more likely to present in a breech position at the time of delivery.
"The most important thing [in determining treatment] is trying to figure out a woman's overall fertility situation, how big the fibroid is, and where it's located," says Dr. Hansard. "If it's in a position where it can interfere with becoming pregnant or maintaining a pregnancy, then based on the size and location we work out what's the best approach."
In most cases, adds Dr. Hansard, this would involve an open incision surgery to excise the fibroid while preserving fertility. However, if fertility isn't a concern, she says other surgical options may be on the table, including laparoscopy, uterine embolization, or hysterectomy.
"A hysterectomy is not optimal for everyone, but the most common reason to have one in the US is uterine fibroids," Dr. Hansard says.
Finally, in some cases you may be able to stop or slow the growth of your fibroid, delaying or even eliminating the need for treatment, with certain medications—Dr. Chang-Jackson says that some forms of hormonal birth control, like the combination pill and the progesterone-only IUD, can provide "first-line symptom management for women with pain and bleeding" due to uterine fibroids.
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