Uterine fibroids are noncancerous growths that develop in the uterus. Frequently appearing during a woman’s reproductive years, these growths are quite common. Uterine fibroids are also known as leiomyomas or myomas. It’s important to understand that fibroids are benign and carry a very low risk of becoming cancerous, nor do they increase the risk of other uterine cancers.
Fibroids can vary significantly in size and quantity. A woman might develop a single fibroid or multiple ones. Some are microscopic, while others can expand to the size of a grapefruit or even larger. Large fibroids can distort the uterus’s shape, both internally and externally. In extreme cases, fibroids can grow so large that they fill the pelvic and abdominal areas, sometimes causing the abdomen to swell and resemble pregnancy.
Many women will experience uterine fibroids at some point in their lives. However, many may not even realize they have them because fibroids often don’t cause any noticeable symptoms. Often, they are incidentally discovered by a healthcare professional during a routine pelvic exam or an ultrasound performed for other reasons, such as during pregnancy.
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Symptoms
Fibroid Locations
Understanding Fibroid Locations: Intramural, Submucosal, and Subserosal
Uterine fibroids are categorized into three primary types based on their location within or on the uterus. Intramural fibroids are the most common type and they develop within the muscular wall of the uterus itself. Submucosal fibroids grow just beneath the uterine lining, bulging into the uterine cavity. Subserosal fibroids project outwards from the outer surface of the uterus. In some cases, both submucosal and subserosal fibroids can be pedunculated, meaning they are attached to the uterus by a stalk, resembling a mushroom hanging inside or outside the uterus.
Many women with uterine fibroids experience no symptoms at all. For those who do, the symptoms experienced can vary based on the size, location, and number of fibroids.
Common symptoms of uterine fibroids may include:
- Heavy menstrual bleeding (menorrhagia) or painful periods (dysmenorrhea): Periods may be significantly heavier than usual, requiring frequent changes of sanitary products, or periods can be accompanied by intense cramping and pain.
- Prolonged or more frequent periods: Menstrual bleeding may last longer than a typical period, or periods may occur more often than the average menstrual cycle.
- Pelvic pressure or pain: A feeling of heaviness or pressure in the pelvic area or persistent pain that can range from mild to severe.
- Frequent urination or difficulty urinating: Fibroids can press on the bladder, leading to a frequent urge to urinate. In some cases, they can obstruct the urethra, making it difficult to empty the bladder completely.
- Enlarged abdomen: Significant fibroid growth can cause the stomach area to visibly expand.
- Constipation: Fibroids pressing on the rectum can lead to bowel movement difficulties.
- Backache or leg pain: Fibroids can press on nerves and muscles in the back and pelvic region, causing pain that radiates to the back or legs.
- Pain during sexual intercourse (dyspareunia): Depending on their location and size, fibroids can cause discomfort or pain during sex.
In rare situations, a fibroid can cause sudden, severe pain if it outgrows its blood supply, leading to tissue degeneration and necrosis.
When to Seek Medical Advice
It’s important to consult a doctor if you experience any of the following:
- Persistent pelvic pain: Pelvic pain that doesn’t subside or worsens over time.
- Heavy or painful periods that disrupt daily life: Menstrual bleeding or pain so severe that it interferes with your normal activities.
- Bleeding or spotting between periods: Any unexpected vaginal bleeding outside of your regular menstrual cycle.
- Difficulty emptying your bladder: Feeling like you cannot fully empty your bladder when urinating.
- Unexplained fatigue and weakness: Persistent tiredness and weakness, which could be symptoms of anemia due to heavy menstrual blood loss.
Seek immediate medical attention if you experience:
- Severe vaginal bleeding: Sudden and excessive bleeding from the vagina.
- Sharp, sudden pelvic pain: Intense and rapidly developing pelvic pain.
Causes
The precise cause of uterine fibroids is not fully understood. However, research suggests several factors that may contribute to their development:
- Genetic Alterations: Many fibroids exhibit genetic mutations that are different from those found in normal uterine muscle cells. These genetic changes may play a key role in fibroid growth.
- Hormonal Influence: Estrogen and progesterone, the two primary hormones driving the menstrual cycle and preparing the uterine lining for pregnancy, also appear to stimulate fibroid growth. Fibroids have a higher concentration of estrogen and progesterone receptors compared to typical uterine muscle cells. This hormonal sensitivity explains why fibroids often shrink after menopause when hormone levels decline.
- Growth Factors: Substances that regulate tissue growth and maintenance in the body, such as insulin-like growth factor, may also influence fibroid development.
- Extracellular Matrix (ECM): The ECM is a complex material that surrounds cells and provides structural support, essentially acting as the “mortar” that holds cells together. Fibroids contain an increased amount of ECM, making them fibrous. The ECM not only provides structure but also stores growth factors and can trigger biological changes within the cells themselves, promoting fibroid growth.
Medical experts believe that uterine fibroids likely originate from a stem cell within the smooth muscle tissue of the uterus (myometrium). A single abnormal cell may undergo repeated division, eventually developing into a firm, rubbery mass that is distinct from the surrounding uterine tissue.
The growth pattern of uterine fibroids is unpredictable. They might grow rapidly, slowly, or remain stable in size for extended periods. Some fibroids experience periods of rapid growth, while others may spontaneously shrink. Fibroids that develop during pregnancy may decrease in size or disappear completely after childbirth as the uterus returns to its normal size.
Risk Factors
While the exact cause remains elusive, certain factors are known to increase the risk of developing uterine fibroids. The primary risk factor is being of reproductive age. Other factors include:
- Race: While fibroids can occur in women of all races, Black women are disproportionately affected. They are more likely to develop fibroids compared to women of other racial groups. Furthermore, Black women tend to develop fibroids at a younger age, are more prone to having larger and multiple fibroids, and often experience more severe symptoms.
- Family History: Having a family history of fibroids, particularly a mother or sister with fibroids, significantly increases your risk of developing them.
- Early Menarche: Starting menstruation before the age of 10 is associated with a slightly higher risk of fibroids.
- Obesity: Being overweight or obese is linked to an increased risk of uterine fibroids.
- Vitamin D Deficiency: Low levels of vitamin D may be associated with a higher risk of fibroids.
- Dietary Factors: A diet high in red meat and low in green vegetables, fruits, and dairy products may increase fibroid risk.
- Alcohol Consumption: Drinking alcohol, including beer, is also linked to a higher likelihood of developing fibroids.
Complications
Uterine fibroids are generally not dangerous, but they can lead to discomfort and various complications.
One of the most common complications is anemia. Heavy menstrual bleeding caused by fibroids can lead to a significant loss of red blood cells, resulting in iron deficiency anemia. Anemia can cause persistent fatigue and weakness. If you experience heavy periods, your doctor may recommend iron supplements to prevent or treat anemia. In severe cases of anemia due to excessive blood loss, a blood transfusion may be necessary.
Fibroids and Pregnancy
Frequently, fibroids do not hinder conception. However, certain types of fibroids, particularly submucosal fibroids that distort the uterine cavity, can potentially contribute to infertility or pregnancy loss.
Fibroids can also elevate the risk of pregnancy complications, including:
- Placental Abruption: This occurs when the placenta, the organ that provides oxygen and nutrients to the developing fetus, prematurely detaches from the uterine wall.
- Fetal Growth Restriction: Fibroids can sometimes interfere with fetal growth, leading to a baby that is smaller than expected for its gestational age.
- Preterm Delivery: There is a slightly increased risk of premature birth (delivery before 37 weeks of gestation) in women with fibroids.
Prevention
Researchers are actively engaged in studying the underlying causes of uterine fibroids to develop effective prevention strategies. Currently, there is no guaranteed way to prevent fibroids. However, the majority of fibroids do not require treatment.
Adopting healthy lifestyle habits may help reduce your risk of developing fibroids or manage their growth:
- Maintain a Healthy Weight: Achieving and maintaining a healthy body weight can be beneficial.
- Regular Exercise: Engaging in regular physical activity is recommended for overall health and may play a role in fibroid prevention.
- Balanced Diet: Consume a balanced diet rich in fruits and vegetables.
Some studies suggest that hormonal contraception, such as birth control pills or long-acting progestin-only contraceptives, might lower the risk of fibroids. However, there’s also some evidence indicating that using birth control pills before the age of 16 might be associated with a slightly increased risk. More research is needed in this area.
Uterine fibroids care at Mayo Clinic
Sept. 15, 2023
References
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