Uterine Fibroids

Uterine fibroids, also known as leiomyomas or myomas, are non-cancerous (benign) growths that develop in or around the wall of the uterus (womb). They are made up mostly of dense, fibrous muscle tissue and can range in size from as small as a seed to as large as a melon, with some growing large enough to distort the shape of the uterus.

Fibroids are extremely common — most women will develop at least one fibroid at some point before menopause, though many never know it because the growths often cause no symptoms at all. When symptoms do occur, they can range from mild discomfort to heavy bleeding, pain, and, in some cases, complications affecting fertility or pregnancy. Understanding what fibroids are, why they form, and what options are available can help women make informed decisions about their reproductive health.

Understanding the Uterus & Where Fibroids Grow

The uterus is a pear-shaped, muscular organ located in the pelvis, made up of three main layers: the endometrium (the inner lining that is shed during menstruation), the myometrium (the thick, muscular middle layer), and the perimetrium (the thin outer covering). Fibroids most commonly arise from the smooth muscle cells of the myometrium, and where they grow relative to these layers determines the type of fibroid and, often, the symptoms it produces.

This distinction matters clinically. A small fibroid growing into the uterine cavity can cause disproportionately heavy bleeding, while a much larger fibroid growing on the outer surface of the uterus may cause no bleeding at all but instead press on nearby organs such as the bladder or bowel.

Types of Uterine Fibroids

Fibroids are classified according to where they develop in relation to the uterine wall:

• Intramural Fibroids: The most common type, growing within the muscular wall of the uterus itself. They can enlarge the uterus and cause heavy bleeding and pelvic pressure as they grow.
• Submucosal Fibroids: Develop just beneath the lining of the uterine cavity and often bulge into the cavity itself. Though less common, they tend to cause the heaviest bleeding and are most strongly linked to fertility problems.
• Subserosal Fibroids: Grow on the outer surface of the uterus and expand outward into the pelvis. They rarely affect menstrual bleeding but can grow quite large and press on the bladder, bowel, or nearby nerves.
• Pedunculated Fibroids: A subtype of submucosal or subserosal fibroids that grow on a thin stalk connecting them to the uterus. Their stalk can occasionally twist, cutting off blood supply and causing sudden, severe pain.
• Cervical Fibroids: A rarer type that develops in the wall of the cervix rather than the main body of the uterus. Depending on size and position, they may affect childbirth or cause pressure symptoms.

More than one type — and more than one fibroid — can be present in the uterus at the same time, which is why fibroids are sometimes described in the plural even in a single patient.

How Common Are Uterine Fibroids?

Uterine fibroids are the most common non-cancerous tumours affecting women of reproductive age. Studies suggest that up to 70 to 80 percent of women will develop at least one fibroid by the age of 50, though the great majority remain small, symptom-free, and are only discovered incidentally during a routine scan or examination for an unrelated reason.

Fibroids are more frequently diagnosed in women in their 30s and 40s, as growth is closely tied to reproductive hormone levels, and they typically shrink after menopause once oestrogen and progesterone levels fall. Asian, including Singaporean, women have historically been reported to have a somewhat lower incidence compared with women of African descent, though fibroids remain one of the most common reasons for a gynaecological consultation locally.

Symptoms of Uterine Fibroids

Many fibroids cause no symptoms whatsoever and are found only during an unrelated pelvic examination or scan. When symptoms do occur, they are usually related to the size, number, and location of the fibroids rather than to fibroids as a whole. Common signs and symptoms include:

• Heavy or prolonged menstrual bleeding: Periods that last longer than seven days or are heavy enough to require frequent changing of pads or tampons, sometimes with visible blood clots, are among the most common complaints and can lead to iron-deficiency anaemia over time.
• Pelvic pain or pressure: A persistent dull ache, heaviness, or feeling of fullness in the lower abdomen, often caused by the fibroid pressing against surrounding pelvic structures rather than by the fibroid itself being painful.
• Frequent or difficult urination: A fibroid pressing on the bladder can reduce its capacity to hold urine, leading to a frequent urge to urinate, while a fibroid pressing on the urethra can occasionally make it difficult to empty the bladder fully.
• Constipation or rectal pressure: Fibroids located toward the back of the uterus can press on the rectum, causing constipation, straining, or a sensation of pressure during bowel movements.
• Abdominal or pelvic swelling: Larger fibroids, or multiple fibroids together, can visibly enlarge the lower abdomen in a manner sometimes mistaken for weight gain or pregnancy.
• Pain during intercourse: Fibroids that distort the shape of the uterus or press against the vaginal wall can cause discomfort or pain during sexual intercourse.
• Lower back pain: Fibroids located on the back wall of the uterus can press against nerves and muscles of the lower back, producing a persistent ache.
• Reproductive difficulties: Depending on their size and location, fibroids — particularly those distorting the uterine cavity — can occasionally make it more difficult to conceive or carry a pregnancy to term.

What Causes Uterine Fibroids?

The exact cause of uterine fibroids is not fully understood, but research points to a combination of hormonal, genetic, and biological factors that influence how and why fibroids form and grow:

• Hormones: Oestrogen and progesterone, the two main hormones responsible for regulating the menstrual cycle, also stimulate the growth of the uterine lining and appear to promote fibroid growth. This is reflected in the way fibroids tend to grow during the reproductive years, when hormone levels are highest, and shrink after menopause, when hormone levels fall.
• Genetic changes: Many fibroids contain genetic alterations that differ from the normal muscle cells of the uterus, suggesting that changes at the cellular level allow certain muscle cells to grow abnormally into a fibroid.
• Family history: Women with a mother or sister who has had fibroids are more likely to develop them, pointing to an inherited genetic predisposition alongside environmental and hormonal influences.
• Other growth factors: Substances that help the body maintain tissue, such as insulin-like growth factor, may affect fibroid growth by promoting the proliferation of fibroid cells and the production of extracellular matrix, the substance that makes fibroids feel firm and rubbery.
• Extracellular matrix (ECM): Fibroids contain an excess of ECM, the structural material that holds cells together. A build-up of ECM not only adds to the size of the fibroid but may also make it more prone to further growth.

Risk Factors for Uterine Fibroids

A number of factors are known to increase the likelihood of developing uterine fibroids:

• Age: The risk of fibroids increases with age during the reproductive years, particularly from the mid-30s onward, and declines again after menopause.
• Family history: Having a close relative, such as a mother or sister, with fibroids increases personal risk, suggesting a genetic component to fibroid development.
• Ethnicity: Fibroids have been reported to occur more frequently, at a younger age, and with more severe symptoms in women of African descent compared with other ethnic groups, though the underlying reasons for this difference are not fully understood.
• Early onset of menstruation: Beginning menstruation at a younger age extends the total number of years of hormonal exposure, which may increase the likelihood of fibroid development.
• Not having children: Women who have never carried a pregnancy to term appear to have a somewhat higher risk, while pregnancy itself may have a temporary protective effect.
• Obesity or high body mass index: Excess body fat can increase circulating oestrogen levels, which may in turn stimulate fibroid growth.
• Diet: Some studies suggest that diets high in red meat and lower in green vegetables and fruit may be associated with a higher risk of fibroids, though more research is needed to confirm a direct causal link.
• Vitamin D deficiency: Emerging research suggests that low levels of vitamin D may be linked to a higher risk of fibroid development, as vitamin D appears to play a role in regulating cell growth within the uterus.

Possible Complications of Uterine Fibroids

Most fibroids do not cause serious complications, but larger or more numerous fibroids can occasionally lead to problems that require closer medical attention:

• Iron-deficiency anaemia: Chronic heavy menstrual bleeding can gradually deplete the body's iron stores, leading to fatigue, dizziness, shortness of breath, and pale skin if left unaddressed.
• Acute pain from fibroid degeneration: A fibroid can occasionally outgrow its blood supply, causing a portion of the tissue to break down. This process, known as degeneration, can cause sudden and sometimes severe pelvic pain along with fever.
• Torsion of a pedunculated fibroid: A fibroid growing on a stalk can twist on itself, cutting off its own blood supply and causing acute, severe abdominal pain that may require urgent treatment.
• Urinary or bowel dysfunction: Fibroids pressing on the bladder or rectum over a prolonged period can occasionally lead to urinary retention, recurrent urinary tract infections, or chronic constipation.
• Pregnancy-related complications: Depending on size and location, fibroids can increase the risk of certain pregnancy complications, including placental abruption, breech presentation, and pre-term delivery, and may occasionally contribute to difficulty conceiving.
• Malignant transformation: The transformation of a benign fibroid into a cancerous growth (leiomyosarcoma) is extremely rare, occurring in a very small fraction of cases, but rapid growth of a fibroid — especially after menopause — is one of the reasons doctors monitor fibroids over time.

Uterine Fibroids, Fertility, and Pregnancy

For most women, fibroids do not prevent pregnancy or cause complications during pregnancy. However, the relationship between fibroids and reproductive health depends heavily on where a fibroid is located rather than simply how large it is.

• Effect on conception: Fibroids that distort the shape of the uterine cavity, particularly submucosal fibroids, can interfere with the implantation of an embryo and are the type most strongly associated with reduced fertility.
• Effect during pregnancy: Fibroids can grow larger during pregnancy in response to rising hormone levels, which may increase discomfort, though many women with fibroids carry an entirely uneventful pregnancy to term.
• Effect on delivery: Large fibroids, or those located low in the uterus near the cervix, can occasionally obstruct the birth canal or affect the position of the baby, which may influence the recommended mode of delivery.
• Postpartum considerations: Fibroids can sometimes contribute to heavier bleeding after childbirth, as they may interfere with the uterus's ability to contract efficiently once the baby and placenta have been delivered.

Women who are planning a pregnancy and have known fibroids, or who experience fertility difficulties, are generally advised to have their fibroids assessed so that any that may affect conception or pregnancy can be identified and managed ahead of time.

How are Uterine Fibroids Diagnosed?

Fibroids are often first detected during a routine pelvic examination, when a doctor notices an irregularity in the shape or size of the uterus. Because many fibroids cause no symptoms, they are also commonly discovered incidentally during imaging performed for an unrelated reason. Where fibroids are suspected, further tests may be used to confirm the diagnosis and map their number, size, and location:

• Pelvic examination: A physical examination in which the doctor feels the shape, size, and contour of the uterus through the abdomen and internally, which can reveal irregularities suggestive of fibroids.
• Ultrasound: The first-line imaging test for fibroids, using sound waves to create an image of the uterus. It can be performed through the abdomen or with a small probe inserted into the vagina for a clearer, closer view.
• Magnetic resonance imaging (MRI): Provides a more detailed picture of the size, number, and exact location of fibroids than ultrasound, and is particularly useful for planning surgery or other procedures in women with larger or multiple fibroids.
• Hysteroscopy: A thin, lighted telescope is passed through the vagina and cervix into the uterus, allowing the doctor to directly visualise and sometimes treat fibroids that are growing into the uterine cavity.
• Saline infusion sonography: A specialised ultrasound in which sterile saline is used to gently expand the uterine cavity, making it easier to detect fibroids that are bulging into the cavity.
• Blood tests: A full blood count may be performed to check for anaemia in women with heavy menstrual bleeding, helping to gauge the impact of fibroids on overall health.

Lifestyle Changes and Self-Management for Uterine Fibroids

While lifestyle changes cannot make an existing fibroid disappear, certain habits may help manage symptoms, support overall hormonal balance, and reduce the risk of new fibroids developing:

• Maintaining a healthy weight: Since excess body fat can raise circulating oestrogen levels, maintaining a healthy weight through balanced nutrition and regular activity may help reduce the hormonal stimulus for fibroid growth.
• Eating a balanced diet: A diet rich in vegetables, fruit, and fibre, with moderate red meat intake, has been associated with a lower risk of fibroids in some studies, and supports general reproductive health.
• Managing iron intake: Women with heavy periods may benefit from iron-rich foods or supplements, taken under medical guidance, to help prevent or correct iron-deficiency anaemia.
• Staying physically active: Regular exercise supports healthy hormone regulation and weight management, both of which may play a role in reducing fibroid-related symptoms over time.
• Tracking your menstrual cycle: Keeping a record of cycle length, bleeding severity, and pain can help both patients and doctors monitor whether symptoms are stable, improving, or worsening over time.