Uterine Fibroids: Non-Cancerous Growths of the Womb

Uterine fibroids are common non cancerous growths formed from smooth muscle and supporting tissue within or around the womb. Many cause no symptoms, while others produce heavy menstrual bleeding, anaemia, pressure symptoms or fertility difficulties. Treatment depends on symptoms, fibroid size and location, future pregnancy plans and personal preference.

What uterine fibroids are Uterine fibroids are benign tumours growing from the smooth muscle of the uterus. Their medical name is uterine leiomyomas, and they are also sometimes called myomas. They contain smooth muscle cells together with variable amounts of firm extracellular matrix and fibrous tissue. Benign means non cancerous. Fibroids do not normally spread to distant organs. Fibroids are different from uterine cancer A fibroid is not the same condition as a uterine sarcoma or cancer of the womb lining. Fibroids are not believed to turn into sarcoma during their usual course. Rare uterine sarcomas are separate tumours that can sometimes resemble fibroids. No scan can identify every rare uterine tumour with complete certainty before tissue examination. Unexpected bleeding after menopause, a new enlarging pelvic mass or concerning systemic symptoms require separate assessment. How fibroids begin and grow Each fibroid appears to develop from one altered smooth muscle cell within the uterine wall. Hormones including oestrogen and progesterone support growth in susceptible tissue. Genetic changes, growth factors and extracellular matrix production also influence development. The exact cause in an individual person usually cannot be identified. Hormonal influence Fibroids usually develop during reproductive years and often become smaller after menopause. Their behaviour is variable, with some growing, some remaining stable and some shrinking over time. Pregnancy can change fibroid size, but growth is not inevitable and does not occur uniformly. Hormonal responsiveness helps explain why several treatments work by suppressing ovarian hormone activity. One fibroid or many A uterus can contain one fibroid or many fibroids of different sizes and locations. They can be microscopic, several centimetres wide or large enough to enlarge the whole abdomen. Symptoms depend more on location, size and number than on the presence of a fibroid alone. A small cavity distorting fibroid can cause heavy bleeding while a large outward growing fibroid may mainly cause pressure. Types are named by location Clinicians describe fibroids according to their relationship with the uterine wall and cavity. The main categories are submucosal, intramural and subserosal fibroids. A single fibroid can cross more than one layer, so real anatomy does not always fit one simple category. The location helps predict symptoms and which treatments are technically possible. Submucosal fibroids Submucosal fibroids grow immediately beneath the womb lining and project partly or completely into the uterine cavity. Even relatively small submucosal fibroids can cause heavy or prolonged menstrual bleeding. They can distort the space where an embryo would implant and have the clearest association with reduced fertility. Many can be assessed and removed through hysteroscopy without an abdominal incision. Intramural fibroids Intramural fibroids grow within the muscular wall of the uterus. They are the most frequently described location and can enlarge or distort the uterine shape. They may contribute to heavy bleeding, cramping, pressure or fertility difficulty depending on size and cavity distortion. The fertility effect of smaller non cavity distorting intramural fibroids remains uncertain and should not be overstated. Subserosal fibroids Subserosal fibroids grow towards the outside surface of the uterus. They often cause pressure or bulk symptoms rather than heavy bleeding unless other fibroids coexist. They generally have less direct effect on fertility because they do not usually distort the uterine cavity. Very large lesions can still alter pelvic anatomy or affect nearby tubes, ovaries, bladder or bowel. Pedunculated fibroids A pedunculated fibroid is attached to the uterus by a narrower stalk called a pedicle. Subserosal fibroids can project into the abdomen on a stalk, while some submucosal fibroids project into the cavity similarly. Rarely, a pedunculated subserosal fibroid can twist around its stalk and lose its blood supply. Sudden severe pain with nausea or vomiting requires urgent assessment for torsion and other acute causes. How common fibroids are Fibroids are among the commonest benign gynaecological tumours. Current RCOG information states that up to two thirds of women develop at least one fibroid during their lifetime. Many remain small and symptom free, so population estimates vary according to age and whether ultrasound screening is used. A common scan finding does not automatically require treatment. Age and reproductive stage Fibroids become more common with increasing age during the reproductive years. They are often diagnosed in the thirties and forties but can occur earlier. Symptoms may become more noticeable as fibroids enlarge or as menstrual patterns change. After menopause, many shrink, although persistent or new symptoms still require assessment. Ethnicity and inequality Black women develop fibroids more frequently, often at a younger age, and may experience larger or more symptomatic disease. Current UK evidence also identifies longer waits and unequal access to diagnosis and treatment. These disparities are not explained by one biological factor and may involve genetics, environment, healthcare access and structural inequality. Ethnicity increases clinical suspicion but does not determine whether any individual person has fibroids. Family history Fibroids occur more commonly when a close biological relative has also had them. Family history suggests inherited susceptibility but does not make development inevitable. Relatives can have very different symptoms, locations and treatment needs. A family history should support earlier consideration rather than create alarm. Why many fibroids cause no symptoms Fibroids can remain outside the cavity and away from sensitive structures. Small stable growths may not change bleeding, uterine contractility or pressure on nearby organs. They are often discovered incidentally during pregnancy imaging or scans performed for another reason. Asymptomatic fibroids usually need information and observation rather than immediate treatment. Heavy menstrual bleeding Heavy menstrual bleeding is the commonest important symptom of uterine fibroids. It means menstrual loss that interferes with physical, emotional, social or practical quality of life. People may describe flooding, clots, prolonged bleeding or needing to change protection unusually frequently. The effect on daily life matters more than trying to estimate blood loss precisely at home. Why fibroids can increase bleeding Several mechanisms probably interact rather than one mechanism explaining every case. Cavity distortion can increase the surface area of endometrium that sheds during menstruation. Fibroids can alter nearby blood vessels and local signals controlling clotting and tissue repair. They can also interfere with coordinated uterine muscle contraction that normally helps compress bleeding vessels. Increased endometrial surface area Submucosal and cavity distorting intramural fibroids can stretch the womb lining over a larger or irregular surface. More lining and irregular shedding can increase the duration or volume of menstrual loss. This explanation is useful but is not sufficient for every person with fibroid related bleeding. Small fibroids can bleed heavily while some large fibroids do not affect menstruation. Altered vasculature Fibroids can change the arrangement, size and function of blood vessels within the uterus and endometrium. Dilated vessels and altered local angiogenic signalling may contribute to heavier or prolonged bleeding. The exact vascular pattern varies by fibroid position and individual biology. Imaging shows anatomy but does not directly measure all microscopic bleeding mechanisms. Impaired uterine contractility The muscular uterus contracts during and after menstrual shedding to limit blood loss. Intramural fibroids can disrupt the direction and coordination of these contractions. Less effective compression of open vessels may prolong bleeding. This mechanism can coexist with increased surface area and altered local haemostasis. Anaemia and iron deficiency Repeated heavy bleeding can deplete iron stores and eventually reduce haemoglobin. Symptoms can include tiredness, breathlessness, palpitations, headaches, dizziness and reduced exercise tolerance. NICE recommends a full blood count for everyone presenting with heavy menstrual bleeding. Ferritin testing may be added when iron deficiency is suspected or according to the local pathway. Painful periods Fibroids can increase menstrual cramping by enlarging the uterus and altering muscle contraction. Submucosal fibroids may also provoke cramping as the uterus attempts to expel cavity contents. Period pain can have several other causes, including adenomyosis and endometriosis. Pain severity alone cannot identify the number, location or size of fibroids. Pressure and bulk symptoms Larger fibroids can create a feeling of pelvic heaviness, pressure or fullness. Symptoms depend on which direction the uterus expands and which neighbouring structures are compressed. The abdomen may appear enlarged, and clothing can feel tighter without overall weight gain. Bulk symptoms can occur without heavy menstrual bleeding. Bladder symptoms A fibroid pressing forwards can reduce the space available for the bladder. This can cause urinary frequency, urgency, night time urination or incomplete emptying. Very large fibroids can occasionally obstruct urinary flow or contribute to recurrent infections. Similar symptoms occur with infection, overactive bladder, pregnancy and pelvic floor disorders. Bowel symptoms A posterior or very large fibroid can press on the rectum or lower bowel. This may contribute to constipation, pressure, painful bowel movements or a sense of incomplete emptying. Constipation can also result from iron tablets, diet, medicines or bowel disorders. Severe vomiting, abdominal distension and inability to pass stool or wind suggests obstruction and needs urgent assessment. Back, hip and leg symptoms A large uterus can alter pelvic mechanics and contribute to lower back or pelvic aching. Pressure on nerves or vessels can occasionally cause pain radiating towards the hip or leg. Back pain remains non specific and commonly has musculoskeletal causes unrelated to fibroids. New weakness, numbness, bladder loss or bowel loss requires urgent neurological assessment. Abdominal enlargement Multiple or large fibroids can enlarge the uterus enough to produce visible abdominal swelling. The swelling may feel firm and can be mistaken for pregnancy or general weight change. A rapidly noticed abdominal mass needs assessment because ovarian, bowel and other pelvic conditions can appear similarly. Examination and imaging identify the organ and likely cause more reliably than appearance. Pain during sex Fibroids can cause deep discomfort during or after penetrative sex, particularly when the uterus is enlarged or tender. Pain can also arise from endometriosis, infection, pelvic floor tension, vaginal conditions or trauma. Assessment should be consensual and sensitive to relationships, sexuality and previous experiences. Nobody should be encouraged to continue painful sexual activity. Fertility and fibroid location Fibroids do not make everyone infertile, and many people conceive without treatment. The effect depends mainly on whether a fibroid distorts the cavity or alters the tubes and pelvic anatomy. Submucosal fibroids have the strongest evidence for reducing implantation and pregnancy rates. Other fertility factors must still be assessed before attributing difficulty entirely to fibroids. Submucosal fibroids and fertility A submucosal fibroid changes the shape and local environment of the uterine cavity. It can interfere with embryo implantation and may increase miscarriage risk. Hysteroscopic removal can improve reproductive outcomes in appropriately selected cases. The decision considers fibroid size, depth, age and the complete fertility assessment. Intramural fibroids and fertility Intramural fibroids that distort the cavity are more likely to impair fertility. Larger non cavity distorting intramural fibroids may also reduce fertility, but evidence is less consistent. Removal is not automatically beneficial for every small intramural fibroid found during fertility investigation. Potential surgical benefit must be balanced against bleeding, adhesions and scarring within the uterine muscle. Subserosal fibroids and fertility Subserosal fibroids generally have little direct effect on implantation because the cavity remains unchanged. Routine removal solely to improve fertility is not usually supported for small asymptomatic subserosal lesions. Very large fibroids can still distort tubes or ovaries and complicate pregnancy or fertility procedures. Treatment remains individualised rather than determined by the label alone. Fibroids and pregnancy Most people with fibroids have uncomplicated pregnancies, but risk depends on size, number and location. Possible associations include pain, miscarriage, abnormal fetal position, preterm birth, placental problems and caesarean birth. A fibroid can obstruct labour or affect the uterine ability to contract after birth in selected cases. Pregnancy care should interpret the scan findings with obstetric history rather than assuming complications are inevitable. Red degeneration in pregnancy Red degeneration occurs when a fibroid's blood supply becomes insufficient, causing tissue infarction and inflammation. It is seen most often during pregnancy and can cause sudden severe localised pain, uterine tenderness and sometimes low grade fever. The presentation overlaps with torsion, placental problems, appendicitis, kidney infection and other acute conditions. Assessment is needed before supportive treatment is chosen. Fibroid torsion Torsion occurs when a pedunculated subserosal fibroid twists around its stalk. The twisting can block venous drainage and arterial blood supply, causing ischaemia and tissue death. This complication is rare but can produce severe focal pain, nausea, vomiting and abdominal tenderness. Urgent surgical assessment may be needed because imaging cannot always distinguish torsion from degeneration. Clinical assessment Assessment begins with the bleeding pattern, pressure symptoms, pain and effect on daily life. The clinician asks about pregnancy possibility, fertility plans, contraception, previous treatment and relevant family history. Intermenstrual bleeding, bleeding after sex and bleeding after menopause require broader assessment. The history guides whether ultrasound, hysteroscopy or another investigation is most appropriate first. Pelvic examination Abdominal examination can identify a firm enlarged uterus or another pelvic mass. With consent, vaginal examination can assess uterine size, shape, mobility and tenderness. A normal examination does not exclude smaller or cavity based fibroids. Internal examination should not proceed without informed consent and an appropriate chaperone offer. Blood tests A full blood count is recommended for all people presenting with heavy menstrual bleeding. The test measures haemoglobin and blood cell patterns but does not identify the cause of bleeding alone. Iron studies can assess depleted iron stores when clinically indicated. Pregnancy testing, thyroid testing or clotting assessment depends on the history rather than being automatic for every fibroid presentation. Ultrasound imaging Pelvic ultrasound is the main imaging method used to confirm and map uterine fibroids. It shows the number, approximate size and location of many fibroids and can identify ovarian or other pelvic findings. Transvaginal ultrasound usually provides detailed views of the uterus when acceptable and suitable. Transabdominal ultrasound can help with a very enlarged uterus or when an internal scan is declined or unsuitable. NICE and first line investigation NICE selects the first investigation according to history and examination rather than using one test for every presentation. Pelvic ultrasound is offered when the uterus is palpable abdominally, a mass is suspected or examination is difficult. If heavy bleeding suggests a submucosal fibroid or another cavity abnormality, outpatient hysteroscopy is preferred first. This distinction prevents ultrasound being presented as universally superior for cavity disease. Hysteroscopy Hysteroscopy uses a thin telescope passed through the cervix to view the inside of the womb. It is the most direct test for submucosal fibroids and other cavity abnormalities. A small fibroid can sometimes be removed during the same visit with prior consent. The procedure can be stopped if pain becomes unacceptable, and alternatives should be discussed beforehand. Magnetic resonance imaging MRI gives detailed information about fibroid number, position, tissue characteristics and vascular relationships. It is not recommended as the routine first investigation for heavy menstrual bleeding. Before uterine artery embolisation or myomectomy, MRI can be considered when ultrasound does not provide enough detail. It is particularly useful for very large, numerous or anatomically complex fibroids. Fibroids found incidentally An incidental fibroid does not prove that it caused the symptom leading to the scan. The clinician checks whether its location and size fit the bleeding, pain or pressure pattern. Other causes can coexist, including adenomyosis, endometriosis, polyps and bowel or bladder disorders. Treatment should target clinically relevant problems rather than the scan report alone. Differential diagnosis Heavy menstrual bleeding can result from adenomyosis, polyps, ovulatory disorders, medicines and bleeding conditions. Pelvic pressure or enlargement can result from ovarian masses, pregnancy, constipation or other abdominal disease. Pain can arise from endometriosis, pelvic infection, ovarian cysts or musculoskeletal conditions. Unexpected bleeding may require assessment of the cervix and womb lining rather than assuming fibroids are responsible. Watchful waiting Treatment is not required when fibroids cause no symptoms or only minimal acceptable symptoms. Watchful waiting means understanding the finding and seeking review if bleeding, pressure, pain or fertility plans change. Routine treatment does not prevent every fibroid from growing or guarantee future symptom avoidance. Many fibroids become smaller after menopause, although new symptoms should still be investigated. Choosing treatment NICE recommends considering fibroid size, number, location, symptom severity, comorbidities and personal preference. Future pregnancy and whether the person wishes to retain the uterus are central decisions. A treatment that preserves the uterus does not always preserve fertility equally well. Shared decision making should compare benefits, limitations, recovery, recurrence and treatment specific risks. Treating iron deficiency Iron replacement treats the consequence of blood loss but does not stop the source of bleeding. Oral iron is commonly used, while intravenous iron may be appropriate when deficiency is severe or tablets are unsuitable. Very low haemoglobin, cardiovascular symptoms or continuing uncontrolled bleeding may require hospital treatment and occasionally transfusion. Bleeding control and iron replacement should usually proceed together. Tranexamic acid Tranexamic acid reduces menstrual bleeding by slowing the breakdown of blood clots within the womb lining. It is taken during bleeding days rather than continuously throughout the cycle. It does not shrink fibroids or prevent pregnancy. Clotting history, kidney function and other medicines can affect whether it is suitable. NSAIDs Non steroidal anti inflammatory drugs can reduce menstrual pain and bleeding for some people. Examples include ibuprofen, naproxen and mefenamic acid. They do not shrink the fibroid itself. Stomach ulcers, kidney disease, cardiovascular risk, asthma and anticoagulant treatment can make them unsuitable. Levonorgestrel intrauterine system The levonorgestrel releasing intrauterine system releases progestogen within the womb and can greatly reduce menstrual bleeding. NICE considers it first line for fibroids smaller than three centimetres when the uterine cavity is not significantly distorted. Distortion can make insertion difficult, increase expulsion risk or reduce effectiveness. Bleeding can be irregular initially, and benefit may take several cycles to become clear. Combined hormonal contraception Combined hormonal contraception can reduce menstrual bleeding and pain while providing contraception. It can be used cyclically or through an extended regimen depending on the product and clinical plan. It does not remove fibroids and may be unsuitable with important clotting, migraine or cardiovascular risks. It is not appropriate when immediate conception is desired. Progestogen options Cyclical oral progestogens are a NICE option for heavy menstrual bleeding. Progestogen only contraception can suppress menstruation and may also reduce bleeding. Individual responses vary, and irregular bleeding can occur. These treatments manage symptoms rather than permanently eliminating fibroids. GnRH agonists Gonadotrophin releasing hormone agonists suppress ovarian hormone production after an initial stimulation phase. They can shrink fibroids temporarily and reduce bleeding before myomectomy or hysterectomy. NICE advises considering pretreatment when fibroids have enlarged or distorted the uterus. Hot flushes, vaginal dryness and bone loss limit duration, and fibroids commonly regrow after treatment stops. Add back therapy Low dose hormonal add back can reduce menopausal symptoms and protect bone during longer ovarian suppression. The precise regimen depends on the medicine, duration and individual risks. Add back therapy does not mean the fibroid treatment has been reversed. Short pre operative agonist treatment may not always require the same approach as longer therapy. Oral GnRH antagonists Current NICE guidance links to selected oral GnRH antagonist treatments for moderate to severe fibroid symptoms. Options include relugolix combined with oestradiol and norethisterone, and linzagolix under its appraisal criteria. They reduce ovarian hormone stimulation and menstrual bleeding without surgery. Eligibility, contraception, bone health and other risks require specialist or experienced prescribing review. Ulipristal acetate restrictions Ulipristal acetate has a very limited role because rare serious liver injury and liver failure have occurred. NICE restricts consideration to selected premenopausal people when surgery and embolisation are unsuitable, unsuccessful or declined. Liver monitoring and detailed counselling are mandatory when it is used. It should not be presented as routine first line fibroid medication. Limits of medical treatment Medicines can reduce bleeding and pain without removing the physical bulk of a large fibroid. NICE warns that pharmacological treatment may be less effective when fibroids are substantially larger than three centimetres. Pressure symptoms and cavity distortion can therefore continue despite improved bleeding. Treatment response should be reviewed rather than continuing an ineffective medicine indefinitely. Hysteroscopic myomectomy Submucosal fibroids projecting into the uterine cavity can be removed through a hysteroscope. No abdominal incision is required, and the procedure can improve bleeding and selected fertility outcomes. Large or deeply embedded fibroids may need more than one procedure or a theatre setting. Risks include bleeding, infection, uterine perforation, fluid complications and intrauterine scarring. Laparoscopic myomectomy Laparoscopic myomectomy removes selected intramural or subserosal fibroids through small abdominal incisions. It is most suitable when the size, number and position allow safe keyhole repair of the uterus. Recovery is usually faster than open surgery, but not every complex uterus can be treated laparoscopically. Fibroid extraction methods and the rare possibility of unexpected malignancy require informed consent. Open myomectomy Open abdominal myomectomy may be needed for very large, numerous or deeply placed fibroids. It allows direct access and strong reconstruction of the uterine wall. Risks include major bleeding, transfusion, infection, adhesions and rarely emergency hysterectomy. Future pregnancy may require additional obstetric planning depending on the depth and location of uterine incisions. Fibroids can recur after myomectomy Myomectomy removes identified fibroids while leaving the uterus in place. New fibroids can develop, and small existing lesions can enlarge later. Recurrence risk varies with age, number of fibroids and follow up duration. The possibility of further treatment should be discussed without presenting recurrence as inevitable. Uterine artery embolisation Uterine artery embolisation is performed by an interventional radiologist using a catheter placed into uterine arteries. Small particles block much of the fibroid blood supply, causing the growths to shrink over following months. It can improve heavy bleeding and bulk symptoms while retaining the uterus. Post procedure pain, infection, discharge, ovarian effects and later reintervention are possible. UAE and future fertility Pregnancy can occur after uterine artery embolisation, but fertility and pregnancy evidence remains less certain than many people expect. Uterine preservation is not identical to proven fertility preservation. People hoping for pregnancy need detailed counselling involving gynaecology, interventional radiology and fertility expertise when appropriate. Myomectomy may be preferred for selected cavity distorting fibroids, but the choice remains individual. Endometrial ablation Endometrial ablation destroys or removes much of the womb lining to reduce heavy bleeding. It does not remove large fibroids or reliably treat pressure symptoms. Some devices can be used with selected small fibroids when the cavity meets technical criteria. Pregnancy afterwards is dangerous, so effective contraception is required and the procedure is unsuitable for future pregnancy plans. Hysterectomy Hysterectomy removes the uterus and permanently prevents fibroid recurrence within it. It is definitive treatment for uterine bleeding and bulk symptoms when other options are unsuitable or unwanted. The operation ends the ability to carry a pregnancy and involves major surgical recovery and complication risks. The ovaries are not automatically removed and require a separate informed decision. Fertility preserving decisions A person wishing to carry a future pregnancy usually avoids hysterectomy and endometrial ablation. Hormonal contraception controls symptoms only while conception is not being attempted. Myomectomy is the established uterine sparing surgical approach when a relevant fibroid should be removed. UAE requires careful counselling because future reproductive outcomes are less certain. Treatment before fertility care Not every fibroid found during fertility assessment requires removal. Submucosal and cavity distorting lesions receive the greatest attention because their reproductive effect is clearest. Semen factors, ovulation, tubal function, age and ovarian reserve must also be considered. A fertility specialist can help avoid unnecessary surgery or delayed treatment. Psychological and quality of life impact Heavy bleeding can create fear of leakage, restricted travel, missed work and difficulty participating in exercise or social life. Abdominal enlargement can affect body image, clothing and confidence. Anaemia, fertility uncertainty and prolonged treatment decisions can produce anxiety or low mood. Emotional support validates the physical condition rather than suggesting symptoms are psychological. Work and practical support Access to toilets, flexible breaks, remote work and time for treatment can reduce disruption. People may need practical planning for heavy bleeding, pain or post procedure recovery. Medical information shared with an employer should remain limited to what is necessary for adjustments. Treatment success should include improved daily function, not only a smaller fibroid measurement. Follow up Follow up depends on symptoms, anaemia, treatment choice and reproductive plans. Persistent bleeding despite treatment requires reassessment of the fibroid and other possible causes. New pressure symptoms can justify repeat examination or imaging. The care plan should explain who to contact if symptoms worsen or pregnancy plans change. Acute severe pain Fibroids usually cause chronic pressure, cramping or recurrent discomfort rather than one sudden catastrophic episode. Abrupt severe focal pain raises concern about torsion, degeneration, cyst complications, pregnancy emergencies or another acute abdomen. Nausea, vomiting, fever, guarding or circulatory symptoms increase urgency. Emergency assessment should establish the cause before the pain is labelled a fibroid flare. Heavy bleeding emergencies Very heavy ongoing bleeding can cause rapid anaemia or circulatory instability. Collapse, severe breathlessness, chest pain, confusion or pale clammy skin requires emergency care. Dizziness, racing heartbeat or inability to manage the bleeding safely requires urgent same day assessment. Pregnancy related bleeding follows a separate urgent pathway. Bleeding after menopause Bleeding after menopause is not considered an expected fibroid symptom without investigation. It requires prompt assessment of the womb lining, cervix and other possible causes. A known history of fibroids should not delay this pathway. Most causes are not cancer, but timely investigation matters. The central safety message Fibroids are benign uterine smooth muscle tumours whose effects depend strongly on size and location. Heavy menstrual bleeding is common, while larger fibroids can cause bladder, bowel and abdominal pressure. Ultrasound maps most fibroids, while hysteroscopy is preferred when a submucosal cavity lesion is suspected. Fertility plans must shape treatment, and sudden severe pain or haemodynamic effects from bleeding require urgent assessment.

Uterine fibroids are common benign smooth muscle tumours. Their location and size determine whether they cause heavy bleeding, pressure or fertility difficulty. Management ranges from observation and bleeding control to embolisation or surgery, with future pregnancy and uterine preservation central to every major decision.