Uterine Fibroids — Causes, Symptoms, Diagnosis & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Uterine fibroids (leiomyomas or myomas) are benign monoclonal tumours arising from uterine smooth muscle (myometrium) that are the most common pelvic tumours in women of reproductive age. They are classified by location: intramural (within the uterine wall — most common), submucosal (projecting into the uterine cavity — most likely to cause heavy bleeding and infertility), subserosal (projecting outward from the uterine surface — can become large), and pedunculated (attached by a stalk). Fibroids are oestrogen- and progesterone-sensitive — they grow during reproductive years, often accelerate during pregnancy, and typically shrink after the menopause. They are benign and extremely rarely (less than 1 in 1,000) undergo malignant transformation to leiomyosarcoma — the distinction cannot be made on imaging alone and requires histology.

The exact cause of uterine fibroids is not fully understood. Each fibroid arises from a single myometrial cell (clonal origin) that has undergone somatic mutations — the most common are in MED12 (mediator complex subunit 12 — affects transcription regulation) and HMGA2 (high-mobility group protein). Oestrogen and progesterone drive fibroid growth — fibroids have higher expression of oestrogen and progesterone receptors than normal myometrium. Risk factors: Black/African ethnicity (approximately 3 times higher incidence and earlier onset than White women — likely due to genetic, hormonal, and environmental factors; higher levels of inflammatory mediators); nulliparity or low parity (pregnancy appears protective against fibroid development); early menarche (before age 10); family history of fibroids (first-degree relative increases risk 2-3 fold); obesity (adipose tissue converts androgens to oestrogen — higher circulating oestrogen); vitamin D deficiency (Black women, who have higher fibroid risk, also have lower vitamin D levels — vitamin D suppresses fibroid cell proliferation in laboratory studies); endocrine-disrupting chemicals (phthalates, BPA exposure associated in epidemiological studies).

Approximately 50% of fibroids are asymptomatic, discovered incidentally on ultrasound or during examination. Symptomatic fibroids present with: Heavy menstrual bleeding (HMB) — the most common symptom; submucosal fibroids distorting the uterine cavity are most likely to cause HMB; can lead to iron-deficiency anaemia; periods are prolonged (more than 7 days) and heavy (saturating pads/tampons, passing large clots). Pelvic pain and dysmenorrhoea — secondary dysmenorrhoea (menstrual cramps worse than baseline), chronic pelvic pressure or heaviness, and acute pain if a pedunculated fibroid undergoes torsion or if red degeneration occurs during pregnancy (haemorrhagic infarction). Pressure symptoms from large fibroids: urinary frequency or urgency (bladder compression), constipation (rectal compression), difficulty emptying the bladder. Subfertility and pregnancy complications: submucosal fibroids (distorting the cavity) impair implantation and increase miscarriage risk; fibroids may cause malpresentation, preterm labour, placental abruption, postpartum haemorrhage, and increased caesarean rate. Abdominal swelling from very large fibroids mimicking pregnancy.

Pelvic examination: enlarged, irregularly shaped uterus with a firm, 'lumpy' or 'lobulated' texture — a clinical finding consistent with fibroids. Pelvic ultrasound (transabdominal and transvaginal): the primary investigation — identifies fibroid location (intramural, submucosal, subserosal), size, number, and relationship to the uterine cavity; transabdominal scans are better for large uteri; transvaginal scanning provides superior resolution for smaller lesions and submucosal fibroids. Saline-infusion sonography (SIS — sonohysterogram): saline instilled into the uterine cavity during ultrasound — outlines the uterine cavity and is superior for detecting and characterising submucosal fibroids and polyps. Hysteroscopy: direct visualisation of the uterine cavity — gold standard for submucosal fibroid assessment; allows biopsy or operative treatment (hysteroscopic myomectomy) at the same time. MRI pelvis: superior to ultrasound for accurately mapping fibroid number, size, position, and blood supply; required before uterine artery embolisation and for distinguishing adenomyosis from fibroids. FBC (iron-deficiency anaemia from chronic HMB), ferritin. Endometrial biopsy (pipelle) if postmenopausal bleeding, abnormal uterine bleeding in women over 45, or if endometrial pathology is suspected.

Watchful waiting: asymptomatic fibroids require no treatment — regular review (annual ultrasound or when symptoms develop) is appropriate. Medical management (symptoms control without addressing fibroid directly): tranexamic acid (antifibrinolytic — reduces HMB by 47-54%; taken during menstruation); NSAIDs (mefenamic acid, naproxen — reduce dysmenorrhoea and HMB by 25-35%); combined oral contraceptive pill or progesterone-only pill (regulate cycles and reduce blood loss); levonorgestrel intrauterine system (Mirena IUS — effective for HMB from intramural and subserosal fibroids; less effective for submucosal fibroids distorting the cavity). Hormonal shrinkage (pre-operative): GnRH analogues (leuprorelin, goserelin — induce a medical menopause; shrink fibroids by 30-60% over 3-6 months; not for long-term use due to bone loss; add-back HRT used to reduce menopausal symptoms; used pre-operatively to reduce surgical blood loss and facilitate minimally invasive surgery). Mifepristone and ulipristal acetate (selective progesterone receptor modulators — SPRMs): reduce HMB and shrink fibroids; ulipristal acetate (Esmya) is currently suspended in the EU/UK due to rare but serious hepatotoxicity cases pending further review. Surgical — myomectomy (fibroid removal with uterus preserved — hysteroscopic myomectomy for submucosal fibroids; laparoscopic or open abdominal myomectomy for intramural/subserosal fibroids; preferred for women wishing to preserve fertility; recurrence rate 15-30% at 5 years). Surgical — hysterectomy (removal of uterus — definitive treatment for fibroids; no recurrence possible; appropriate for women who have completed their family and have severe symptoms). Uterine artery embolisation (UAE): interventional radiology procedure — bilateral occlusion of the uterine arteries with embolic particles causes fibroid infarction and shrinkage (approximately 50-60% reduction in fibroid volume); treats HMB effectively in approximately 80-90% of patients; uterus preserved; suitable for women not wishing surgery and those with multiple/large fibroids; fertility outcomes post-UAE are less well-established than post-myomectomy. MRI-guided focused ultrasound (MRgFUS) and radiofrequency ablation: emerging minimally invasive techniques with growing evidence.

No proven prevention exists for uterine fibroids, as their aetiology is primarily genetic and hormonal. Maintaining a healthy BMI reduces circulating oestrogen from adipose tissue, which may slow fibroid growth. Vitamin D supplementation in deficient women may reduce fibroid growth (laboratory evidence; limited clinical trial data currently available). Hormonal suppression (GnRH analogues, combined hormonal contraceptives, Mirena IUS) can slow fibroid growth and control symptoms but is not preventive. After myomectomy: the combined oral contraceptive pill, progestogen, or Mirena IUS may reduce recurrence risk (limited RCT evidence). Avoid smoking, maintain healthy diet rich in fruits, vegetables, and fish, and limit red meat consumption — associated with lower fibroid risk in epidemiological studies. Vitamin D optimisation and reduction of endocrine disruptor exposures are areas of active research.

Iron deficiency anaemia is the most common complication — from chronic heavy menstrual blood loss caused by submucosal and intramural fibroids; severe anaemia may require blood transfusion before definitive treatment. Urinary complications from large fibroids include chronic urinary retention, ureteric compression, hydronephrosis, and obstructive nephropathy. Pregnancy complications associated with significant fibroids include miscarriage (particularly with submucosal fibroids), preterm labour, placental abruption, malpresentation, postpartum haemorrhage, and higher caesarean section rates. Fibroid degeneration during pregnancy (red degeneration — haemorrhagic infarction due to rapid growth) causes severe acute pain requiring hospitalisation and analgesia. Social and occupational impairment from chronic pain and heavy bleeding significantly affects quality of life. Extremely rarely (less than 1 in 1,000 fibroids), malignant transformation to leiomyosarcoma occurs — this cannot be reliably distinguished from benign fibroids on MRI alone and requires histological confirmation; rapidly enlarging fibroids in postmenopausal women require urgent investigation.

Consult your GP for: heavy menstrual bleeding (regularly soaking through a pad or tampon within 1-2 hours, passing large clots, or periods lasting more than 7 days), severe menstrual pain, pelvic pressure or pain, urinary frequency not explained by infection, abdominal swelling, or subfertility. See your doctor urgently for: sudden severe pelvic pain (possible pedunculated fibroid torsion or red degeneration in pregnancy), significant anaemia symptoms (severe fatigue, breathlessness, palpitations from iron deficiency). If fibroids have been diagnosed and you are planning pregnancy, seek pre-pregnancy gynaecology review to discuss whether myomectomy or other treatment is appropriate before conception — submucosal fibroids significantly impair fertility and should generally be treated. Any postmenopausal woman with newly discovered or enlarging uterine masses requires urgent investigation to exclude uterine malignancy.