Uterine fibroids develop when a single muscle cell in the uterine wall begins dividing abnormally, eventually forming a firm, round growth. About 70% of women of reproductive age will develop at least one fibroid, though only about a quarter of those experience symptoms that need treatment. No one thing “gives” you fibroids. They result from a combination of genetic changes inside uterine cells, hormones that fuel their growth, and a range of risk factors that raise your chances.
What Happens Inside the Uterus
Each fibroid starts as a single cell that acquires a genetic mutation and begins to multiply on its own. The most common trigger is a mutation in a gene called MED12. A Johns Hopkins systematic review found that roughly 56% of all fibroids carry this specific mutation, with individual studies reporting rates anywhere from 31% to 80%. The mutation disrupts normal cell signaling, essentially removing one of the brakes on cell growth.
Once that rogue cell starts dividing, hormones take over as the primary fuel. Estrogen and progesterone, the two hormones that rise and fall with every menstrual cycle, both promote fibroid growth. Progesterone in particular plays a surprisingly active role: it increases blood supply to the growing fibroid, stimulates the production of growth factors, and helps build up the dense, fibrous tissue that gives fibroids their firm texture. Fibroid cells actually have higher levels of progesterone receptors than normal uterine muscle, which means they respond more intensely to the same hormones circulating through the rest of your body.
This is why fibroids are a disease of the reproductive years. They grow when hormone levels are high, and they tend to shrink and sometimes resolve entirely after menopause, when estrogen and progesterone drop off.
Risk Factors You Can’t Control
Family history is one of the strongest predictors. If your mother or sister had fibroids, your risk is significantly higher. This likely reflects inherited differences in how uterine cells respond to hormones and how easily they accumulate the mutations that spark fibroid growth.
Race plays a major role. Black women develop fibroids more frequently, at younger ages, and with greater symptom severity than white women. Research points to a combination of biological susceptibility and the cumulative impact of social and structural factors, including chronic stress, differences in healthcare access, and higher lifetime exposure to certain environmental chemicals. Black women with fibroids also tend to experience worse clinical and surgical outcomes.
Age matters in a straightforward way: the prevalence of fibroids climbs steadily from the late 20s through the 40s, peaking just before menopause. Starting your period at an early age also raises your risk, because it means more total years of cyclical hormone exposure to the uterine lining and muscle.
Lifestyle and Dietary Factors
Obesity is consistently linked to fibroids. Fat tissue produces its own estrogen, so carrying extra weight raises the overall estrogen level your uterine cells are exposed to. This creates a more favorable environment for fibroid growth and may help explain why weight loss sometimes slows their progression.
Diet appears to play a role, though the evidence is strongest for a few specific patterns. A diet high in red meat and low in green vegetables, fruit, and dairy has been associated with higher fibroid risk in multiple studies. The exact mechanism isn’t fully understood, but it may involve the way certain foods influence estrogen metabolism or inflammation.
Alcohol is a more complicated picture. A large meta-analysis covering over 135,000 women found no significant overall link between drinking and fibroid risk. However, subgroup analyses revealed a notably higher risk among women in China, and studies that confirmed fibroids through surgery rather than imaging also showed a modest increase. So while moderate drinking doesn’t appear to be a major driver for most women, the relationship may depend on other factors like genetics and overall diet.
Vitamin D Deficiency
Low vitamin D levels show up repeatedly in fibroid research. A large genetic analysis of nearly 450,000 samples found that higher predicted vitamin D levels were associated with a small but statistically significant reduction in fibroid risk. Women with diagnosed fibroids are more likely to be vitamin D deficient than women without them, and lab studies suggest vitamin D may help slow fibroid cell growth and reduce the buildup of fibrous tissue. This connection is particularly relevant for Black women, who have higher rates of both vitamin D deficiency and fibroids.
Environmental Chemical Exposure
Certain industrial chemicals that mimic or interfere with hormones may contribute to fibroid development. Lab and animal studies have shown that chemicals commonly found in plastics, personal care products, and food packaging can activate the same biological pathways involved in fibroid growth. These include compounds found in soft plastics (like DEHP, a type of phthalate), BPA from hard plastics and can linings, and diethylstilbestrol, a synthetic estrogen once prescribed during pregnancy. The evidence in humans is still building, but the biological plausibility is strong: if fibroids are hormone-driven, chemicals that disrupt hormonal signaling could plausibly nudge that process along.
Why Fibroids Grow and Shrink Over Time
Because fibroids depend on hormones, their behavior tracks closely with hormonal shifts in your life. They often grow faster during pregnancy, when estrogen and progesterone surge. They may also grow during perimenopause, when hormone levels fluctuate unpredictably, sometimes spiking before they eventually decline. Hormonal birth control can affect fibroid growth in either direction depending on the type and the individual.
After menopause, fibroids lose their primary fuel source. Most shrink substantially, and many resolve completely. This is why treatment decisions often factor in how close you are to menopause. A woman in her late 40s with manageable symptoms may choose to wait it out, while someone in her early 30s facing the same fibroids has potentially 15 or more years of hormone-driven growth ahead.
Multiple Factors Working Together
The honest answer to “how do you get fibroids” is that several things have to line up. A cell in your uterus acquires a mutation. Your hormonal environment feeds its growth. Your genetic background, race, body composition, vitamin D status, diet, and possibly chemical exposures all influence how aggressively that growth proceeds and whether you ever notice symptoms. Most women with fibroids have several of these factors at play, and no single one is enough on its own to guarantee you’ll develop them.
What this means practically is that while you can’t change your genetics or family history, the modifiable factors, maintaining a healthy weight, eating more fruits and vegetables, checking your vitamin D levels, and reducing unnecessary exposure to hormone-disrupting chemicals, are all reasonable steps that align with what the research currently shows.