Fibroids 101

Maybe you were recently diagnosed with uterine fibroids. Maybe you suspect you have them but have not been diagnosed. Or maybe you’ve been living with them for a while and are now considering treatment. No matter where you are in your journey, it’s good to understand what you’re dealing with so you’re informed when you take your next steps.

Let’s start at the beginning—what are fibroids?
Fibroids are made of muscle cells and other tissues that grow in and around the wall of the uterus, or womb. They’re also called leiomyoma or just myoma.

Fibroids are tumors, but that doesn’t mean they are cancerous—in fact, they are almost always benign (not cancerous).1 Uterine fibroids are the most common benign tumors in women of childbearing age.2

There is no formula for fibroids when it comes to number or size. You can have a single fibroid or multiple ones, and they can vary in size from as small as an apple seed to as big as a grapefruit.1

What causes fibroids?
The truth is we’re not completely sure what causes fibroids. Researchers think that more than one factor could play a role. These factors could be genetic (run in families) and hormonal (affected by estrogen and progesterone levels).1 Fibroids grow rapidly during pregnancy when hormone levels are high. And they tend to shrink after menopause due to a decrease in hormone production.1

What are the symptoms of fibroids?
Sometimes there aren’t any. Many women have uterine fibroids sometime during their lives, but they may not know it because fibroids often cause no symptoms. Your doctor may discover fibroids incidentally during a pelvic exam or prenatal ultrasound.3

Fibroid tissue on its own can be harmless, but for some women, fibroids can cause severe discomfort and take a toll on their daily lives.3 Symptoms can include1:

  • Heavy, painful periods
  • Anemia
  • Bloating
  • Frequent urination
  • Pain during sex
  • Lower back pain

How common are fibroids?
Very. Up to 80% of women develop fibroids by the age of 50.1 Here are some factors that can increase your risk1:

  • Age—Fibroids become more common as you age, especially during your 30s and 40s through menopause. After menopause, fibroids usually shrink.
  • Family history—Having a family member with fibroids increases your risk. If your mother had fibroids, your risk is about three times higher than average.
  • Ethnicity—African American women are more likely to develop fibroids than white women.
  • Obesity—Women who are overweight are at higher risk. For very heavy women, the risk is two to three times greater than average.

To summarize, fibroids are tricky.
We’re not sure what causes them, and they vary in number, size, and symptoms. What we do know is they can cause discomfort and disruption, and you should let your doctor know if you are experiencing the symptoms outlined above—especially if you have any of the risk factors. The (very!) good news is that fibroids can be treated, and your doctor can tell you what options are available to you.

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  1. U.S. Department of Health & Human Services Office on Women’s Health. Uterine fibroids. Accessed February 22, 2022.
  2. Medline Plus. National Library of Medicine. Uterine fibroids. Accessed February 22, 2022.
  3. Mayo Clinic. Uterine fibroids. Accessed February 22, 2022.