Causes and Risk Factors of Uterine Fibroids

The causes of uterine fibroids are unknown, but there is evidence that multiple factors–such as race, age, family history, the number of micronutrients, and stress—play a role in their growth. 

Black women are especially burdened by fibroids. Not only are Black women more likely to get fibroids and experience severe symptoms, but they often get treatment later or may get inappropriate treatment due to systemic racism and implicit bias in the U.S. healthcare system.

This leads to earlier deterioration of health and quality of life. The cumulative impact of economic, psychosocial, and environmental stresses and the role it plays in the deterioration of a Black woman's overall health must be discussed when we think about fibroids and Black health.

This article discusses the causes of uterine fibroids, with insights into the effects on Black women.

Common Causes

Researchers have come up with a number of theories to explain the cause of uterine fibroids, but they have yet to arrive at a definitive answer.

What we do know is that they are under hormonal control—namely estrogen and progesterone.

Fibroid growth varies in pregnancy, but if they do grow this is more likely to happen in the first trimester. They may also stop growing or shrink once a woman reaches menopause, although this occurs less frequently in Black women for unknown reasons.

While the definitive cause of uterine fibroids is unknown, most medical professionals believe that there are many different factors at play. Some potential causes include:

• Hormones: Unopposed estrogen levels have been shown to promote fibroid development. High progesterone levels have also been associated with increases in fibroid growth.
• Genetics: Genetic mutations in the MED12, HMGA2, COL4A5/COL4A6, or FH genes have all been implicated in the development and growth of uterine fibroids.
• Family history: Having a family member with fibroids increases your risk of developing fibroids in your lifetime. In fact, if your mother had fibroids, you are three times more likely to have fibroids compared with a woman with no family history of fibroids, highlighting the strong genetic component of this condition. More research needs to be done to elucidate the genetic factors that contribute to this condition.
• Growth hormones: Hormones such as insulin-like growth factors, epidermal growth factors, and transforming growth factors may also play a role in fibroid development.
• The number of micronutrients in your blood: The amount of certain micronutrients, such as low iron and/or vitamin D levels, may contribute to the growth of fibroids
• Major stress: Some studies have cited stressful life events and possibly childhood abuse as possible triggers of uterine fibroid development.

The reasons for the disparities are unclear, although research offers some clues. Fibroids have been associated with the following risk factors:

• African ancestry: Black women are two to three times more likely to develop fibroids than White women, but healthcare providers don’t know why. Several studies have hypothesized that obesity and non-modifiable risk factors such as race or genetic ancestry may interact to jointly influence uterine fibroid growth, but most existing studies have not evaluated their interaction.
• Age: Development of fibroids increases with age, but symptoms tend to diminish since tumors regress after menopause.
• Obesity: A large meta-analysis found that women who are obese were 17% to 26% more likely to have uterine fibroids, although the cause-and-effect link between the two is unknown. Other studies have found that the risk of women who are obese developing fibroids is two to three times greater than that of women who are of average weight. This is especially the case with those who have central obesity, or higher amounts of belly fat. Fibroid growth is triggered by estrogen, which can be overproduced by excess abdominal fat. 
• Family history of uterine fibroids
• High blood pressure
• No history of pregnancy: Women who have never been pregnant or have been pregnant two or fewer times are more likely to develop symptomatic fibroids.
• High stress levels
• Vitamin D deficiency: Women with darker-pigmented skin tones are more likely to experience vitamin D deficiency, which some studies have associated with an increased risk of uterine fibroid development. 

Definitively, there are factors that have been shown to lower the risk of fibroids, such as:

• Pregnancy (the risk decreases with an increasing number of pregnancies)
• Long-term use of oral or injectable contraceptives

Genetics

Uterine fibroids are the most common pelvic tumor in women of childbearing age, but their cause remains a mystery. Fortunately, some recent genetic studies have led to some hope for answers. 

Cytogenetic studies—which study DNA—have found that up to 40% of uterine fibroids bear some chromosomal abnormalities.

Uterine fibroids arise from an uncontrolled overgrowth of smooth muscle and connective tissue in the uterus. The two components that contribute to this overgrowth are a transformation of normal smooth muscle cells, also known as myocytes, to abnormal smooth muscle cells and their growth into clinically apparent tumors.

The identity of the factors and molecular mechanisms involved in the cellular transformation of myometrial cells into uterine fibroids is unknown, but our knowledge of tumor formation in cancer cells is a strong foundation to build off of.

The development of uterine fibroids involves a complex interaction among genes and environment, but the degree to which this plays a role in disease severity is unknown—leaving many women, especially Black women, searching for answers. 

Research studying affected women and their first-degree relatives who also have uterine fibroids is essential to deciphering the genetic components of uterine fibroids.

This research also needs to be inclusive, with robust and equal representation among women of different races and ethnicities. The availability and examination of such individuals not only hastens cytogenetic and molecular studies but also serves as a crucial component in dissecting and defining the genetic loci that contribute to the development of uterine fibroids.

It is the hope of the scientific community that by understanding and uncovering the genetic and environmental mechanisms responsible for uterine fibroids, future gene therapies may be designed. 

Lifestyle Factors

The following modifiable lifestyle factors have been shown to change your risk for having uterine fibroids:

• Stress: Some preliminary research has linked high stress levels and fibroid symptomatology. Relaxation techniques like yoga, massage, tai chi, and acupuncture have been reported as effective means of not only managing stress but relieving pain as well. 
• Obesity: Maintaining a healthy weight, exercising, and avoiding foods high in sugar, sodium, or calories has been shown to halt the growth of current fibroids and stop the development of new ones.
• High blood pressure: Studies suggest that the presence of uterine fibroids is associated with increased blood pressure levels, and the prevalence of hypertension in women with uterine fibroids has been shown to be as high as 40%.
• Red meat intake: High red meat intake has been associated with higher fibroid prevalence, but the causal link between the two is unknown. Still, health professionals suggest limiting red meat consumption for its overall health benefits.
• Food additive consumption: Avoiding processed foods, especially those high in sugar, sodium, or calories, has been shown to help stop the growth of current and new fibroids. Some even encourage eating a special fibroid diet high in natural fruits and vegetables.
• Use of soybean milk: High soybean consumption is associated with a high risk of uterine fibroids because soybeans contain phytoestrogen, which can raise estrogen levels. 

Effect on Black Women

The disproportionate impact of fibroids on Black women is no secret, and the lack of consensus on its causes and treatment puts Black women at an even greater disadvantage.

Lower socioeconomic status, higher obesity rates, less access to care, and medical mistrust are just a few of the obstacles further standing in the way. 

The propagation of untrue myths about Black pain and neglecting the concerns of Black women have also led some women to normalize their pain. As a result, some Black women are reluctant to engage with the U.S. healthcare system.

Unsurprisingly, these obstacles increase the likelihood of Black women showing up to a clinic with:

• More severe symptoms
• Poorer overall health
• Greater need for more invasive treatment

Of note, while Black women are most affected by fibroids, they are often one of the least represented groups in research studies.

A review of 106 studies cited in the Agency for Healthcare Research and Quality (AHRQ) report on uterine fibroids found that nearly one in four studies on uterine fibroids did not include data on the patients’ ethnicity or race. In the studies that did, Black women made up only 15% of study participants.

Frequently Asked Questions

What causes Black women to develop uterine fibroids? 

The main causes of uterine fibroids in Black women are unknown, but it is likely a combination of many factors, such as genetic, environmental, and lifestyle factors. Vitamin D deficiency and hereditary factors have been spotlighted due to the race-based differences that exist in disease prevalence. 

What makes fibroids flare up? 

Fibroids can flare up for a number of reasons, including:

• During sexual intercourse
• Bowel movements
• Exercise
• Your period

The symptoms can be so painful that they wake you up at night or impact your ability to complete normal daily activities.

Do fibroids cause miscarriages? 

The size and type of fibroid determine how likely your fibroid is to impact your fertility:

• If a fibroid is closer to the middle of the uterus, where an embryo is more likely to implant, it is more likely to cause a miscarriage.
• If a fibroid is very large or if you have multiple fibroids, they can distort your anatomy, block your fallopian tube, increase your risk of miscarriage and affect your fertility in general.

A Word From Verywell

If you have fibroids, you don’t have to give up activities you enjoy. We understand that those with symptomatic fibroids cannot escape their presence and that finding answers can be frustrating, especially for Black women, who face many obstacles in obtaining equal and appropriate health care. While healthcare providers don’t have all the answers, there are many viable treatments to help mitigate or eliminate fibroids, so we encourage you to get the help you need.

Eliminating systemic racism and socioeconomic gaps is integral to lessening all health gaps, especially the uterine fibroid health gap.

Including Black women in research is central to this process. Inclusive research broadens our medical knowledge and provides us with an opportunity to create more personalized treatment plans that address the unique challenges Black women face. Complicating the process even more is that many Black women with fibroids appear to choose to suffer in silence.

Fortunately, the future of uterine fibroid research has never looked brighter given the increases in medical technology and a renewed spotlight on fibroids' mental and emotional toll.