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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Benign monoclonal tumours of uterine smooth muscle. Affect 20–40% of women of reproductive age
- Classification by location: subserosal (outer surface), intramural (within myometrium — most common), submucosal (projects into cavity — most symptomatic)
- Symptoms depend on size and location: HMB (especially submucosal), pelvic pressure, urinary frequency, subfertility
- Oestrogen-dependent: grow in reproductive years, shrink after menopause
- Medical management: LNG-IUS (if cavity not distorted), tranexamic acid, GnRH agonists (pre-surgical shrinkage)
- Surgical: myomectomy (fertility-preserving), UAE (interventional radiology), hysterectomy (definitive)
Overview
Uterine fibroids (leiomyomas) are benign monoclonal tumours arising from the smooth muscle of the myometrium. They are the most common solid pelvic tumour in women. Fibroids are oestrogen- and progesterone-dependent, growing during the reproductive years and typically regressing after menopause. They are classified by location: intramural (within the myometrial wall — most common), submucosal (projecting into the uterine cavity — most likely to cause HMB and subfertility), and subserosal (projecting from the outer surface of the uterus — more likely to cause pressure symptoms).
Epidemiology
Fibroids affect approximately 20–40% of women during their reproductive years and are 2–3 times more common in women of African-Caribbean descent. Many fibroids are asymptomatic and discovered incidentally. Risk factors include increasing age (until menopause), African-Caribbean ethnicity, nulliparity, early menarche, obesity, and family history. Protective factors include increasing parity and combined oral contraceptive use.
Clinical Features
Symptoms
Heavy menstrual bleeding (especially submucosal fibroids) — the most common symptom
Pelvic pressure or heaviness
Urinary frequency or retention (anterior fibroid pressing on bladder)
Constipation (posterior fibroid pressing on rectum)
Dysmenorrhoea
Subfertility (submucosal fibroids distorting cavity)
Acute severe pain (red degeneration in pregnancy, or torsion of pedunculated fibroid)
Signs
Enlarged, irregularly shaped (bosselated), firm, non-tender uterus on bimanual examination
Palpable abdominal mass if large
Pallor (iron deficiency anaemia from HMB)
Investigations
First-line
Pelvic USS (TVUSS)First-line imaging — confirms diagnosis, number, size, and location of fibroids. Well-circumscribed, hypoechoic lesions
FBCCheck for iron deficiency anaemia
Second-line
MRI pelvisIf large fibroids, multiple fibroids, or planning surgery/UAE — superior anatomical delineation
HysteroscopyTo assess submucosal fibroids and suitability for hysteroscopic resection
Specialist
Endometrial biopsyIf age >45, IMB, or suspicious features — exclude endometrial pathology
1
Asymptomatic fibroids
- No treatment required — reassure and monitor
- Will shrink naturally after menopause
2
Medical management
- Fibroids <3 cm or not distorting cavity: LNG-IUS first-line for HMB
- Tranexamic acid 1 g TDS and/or mefenamic acid 500 mg TDS during menses
- GnRH agonists (goserelin/leuprorelin): shrink fibroids by ~50%. Use pre-operatively for 3–6 months to reduce fibroid size and correct anaemia. Max 6 months without HRT add-back
- Relugolix (oral GnRH antagonist with add-back): newer option for fibroid-related symptoms
3
Surgical management
- Hysteroscopic myomectomy: for submucosal fibroids — minimally invasive, preserves fertility
- Laparoscopic/open myomectomy: for intramural/subserosal fibroids — fertility-preserving
- Uterine artery embolisation (UAE): interventional radiology procedure. Shrinks fibroids by cutting blood supply. NOT recommended if future pregnancy desired
- Hysterectomy: definitive treatment. Consider if family complete and other options have failed
Complications
- Iron deficiency anaemia: From chronic HMB
- Red degeneration: Acute haemorrhagic infarction of fibroid, typically in pregnancy — severe pain, tenderness, low-grade fever. Manage conservatively with analgesia
- Subfertility: Submucosal fibroids distort cavity and impair implantation
- Pregnancy complications: Miscarriage, malpresentation, preterm labour, PPH, obstructed labour
- Sarcomatous change: Extremely rare (<0.5%) — leiomyosarcoma. Suspect if rapidly enlarging postmenopausally
UKMLA Exam Tips
- 1Submucosal fibroids → HMB and subfertility (cavity distortion). Most symptomatic type
- 2Intramural = most common type. Subserosal = pressure symptoms
- 3GnRH agonists shrink fibroids pre-operatively but cause temporary menopause — max 6 months
- 4Red degeneration in pregnancy: acute pain + fibroid + pregnancy. Manage conservatively
- 5Fibroids are oestrogen-dependent: grow in pregnancy, shrink after menopause
- 6UAE is NOT suitable if future pregnancy is desired — may compromise uterine blood supply
- 7Rapid growth postmenopausally → suspect leiomyosarcoma (very rare)
practicetest your knowledge on uterine fibroidsApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — obstetrics and beyond.
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