What is abnormal uterine bleeding and what is a normal cycle?
Abnormal uterine bleeding (AUB) is bleeding from the uterus, outside pregnancy, in a woman of reproductive age that is abnormal in frequency, regularity, duration or volume. Up to one-third of women experience it, most often around menarche and perimenopause. Bleeding after menopause is assessed separately as postmenopausal bleeding.
| Parameter | Normal | Abnormal |
|---|---|---|
| Frequency | 24–38 days | Frequent (under 24 days), infrequent (over 38 days) or absent (amenorrhoea) |
| Regularity | Cycle-to-cycle variation of about ±2 to 7 days | Irregular — variation over 20 days |
| Duration | 8 days or less | Prolonged — over 8 days |
| Volume | 5–80 mL | Heavy (over 80 mL, or enough to affect quality of life); light (under 5 mL) |
AUB is also divided into acute (bleeding heavy enough to need immediate intervention) and chronic (abnormal bleeding for most of the previous 6 months). Acute bleeding can occur on its own or on top of chronic AUB.
How did FIGO change AUB terminology?
AUB terminology was revised in 2007, and FIGO published updates in 2011 and 2018. FIGO System 1 defined the normal and abnormal limits of frequency, regularity, duration and volume. FIGO System 2 introduced PALM-COEIN to classify causes.
| Abandoned term | Current term |
|---|---|
| Menorrhagia | Heavy menstrual bleeding (HMB) — over 80 mL, or heavy enough to interfere with quality of life |
| Metrorrhagia | Intermenstrual bleeding — cyclical or random bleeding between periods |
| Oligomenorrhoea | Infrequent menstrual bleeding (cycle over 38 days) |
| Bleeding on hormone therapy | Breakthrough bleeding (BTB) |
What is the PALM-COEIN classification?
PALM causes are structural — they can be seen on imaging or histology. COEIN causes are non-structural and are found mainly by history and laboratory tests. More than one cause can coexist, and a structural lesion seen on scan is not always the cause of the bleeding.
| Letter | Cause | Key features |
|---|---|---|
| P | Polyp (AUB-P) | Endometrial or endocervical focal outgrowth; often intermenstrual bleeding; mostly benign |
| A | Adenomyosis (AUB-A) | Endometrial tissue within the myometrium; heavy, painful or prolonged periods; enlarged uterus |
| L | Leiomyoma (AUB-L) | Fibroids; heavy or prolonged bleeding, especially if large or submucosal; many are asymptomatic |
| M | Malignancy and hyperplasia (AUB-M) | Endometrial hyperplasia or cancer; unpredictable bleeding; risk from unopposed oestrogen |
| C | Coagulopathy (AUB-C) | Systemic bleeding disorders such as von Willebrand disease — common in adolescents and young women with HMB |
| O | Ovulatory dysfunction (AUB-O) | PCOS, hypothalamic causes, thyroid disease; infrequent, irregular, heavy or prolonged bleeding |
| E | Endometrial (AUB-E) | Local failure of endometrial haemostasis (inflammation, infection, vasoconstriction defects) |
| I | Iatrogenic (AUB-I) | Hormonal contraceptives, anticoagulants, tamoxifen; anticoagulant-related AUB is now classed here |
| N | Not otherwise classified (AUB-N) | Arteriovenous malformation, chronic endometritis, caesarean scar defect |
How is a woman with abnormal uterine bleeding evaluated?
- Check haemodynamic stability first — resuscitate an unstable patient with acute AUB before taking a full history.
- History — frequency, regularity, duration, volume (pad changes, clots, night-time flooding), intermenstrual or postcoital bleeding, drugs, contraception.
- Examination — signs of anaemia, thyroid disease, hyperandrogenism; speculum and bimanual examination.
- Exclude pregnancy in every woman of reproductive age (urine or serum hCG) and check a complete blood count.
- Targeted tests — thyroid function if symptoms or no other cause; prolactin and androgens only if an endocrine cause is suspected; ferritin in HMB.
- Bleeding-disorder screen — platelet count, PT and aPTT; these can be normal in von Willebrand disease, so refer to haematology if suspicion remains.
Imaging. Transvaginal ultrasound is the usual first-line scan for structural causes (transabdominal may suit adolescents). Saline-infusion sonography helps detect intracavitary lesions, and MRI is reserved for when ultrasound is inadequate — for example complex fibroids or adenomyosis. NICE NG88 advises offering outpatient hysteroscopy when the history suggests submucosal fibroids, polyps or endometrial pathology, and pelvic ultrasound when the uterus is palpable abdominally, a pelvic mass is suspected or examination is inconclusive.
When is endometrial sampling needed?
StatPearls recommends endometrial sampling for women aged 45 years or older with AUB, because age is a major risk factor for endometrial cancer. Younger women also need sampling if bleeding persists, if there is a history of unopposed oestrogen exposure, or if medical treatment fails.
- Office endometrial biopsy is the first-line method.
- Hysteroscopy with dilatation and curettage if office sampling fails, is inadequate or cannot be done.
- Hysteroscopy if symptoms persist despite a normal biopsy, since blind sampling can miss focal lesions such as polyps.
- NICE NG88 goes further for HMB: take endometrial samples only during diagnostic hysteroscopy and do not offer 'blind' biopsy.
How is chronic heavy menstrual bleeding treated medically?
Treatment is needed when AUB causes anaemia or affects quality of life, and it depends on the cause, fertility and contraceptive wishes, comorbidities and patient preference. NICE NG88 recommends considering a levonorgestrel-releasing intrauterine system (LNG-IUS) as the first treatment for HMB when there is no identified pathology, fibroids under 3 cm that do not distort the cavity, or suspected or diagnosed adenomyosis.
| Option | Typical regimen | Blood-loss reduction / notes |
|---|---|---|
| LNG-IUS | 19.5–52 mg device for 5 years | 71–95%; comparable to hysterectomy in quality-adjusted life years |
| Combined oral contraceptive | Monophasic 30–35 µg oestrogen pill daily | 35–69%; also regulates ovulatory dysfunction |
| Continuous progestins | Medroxyprogesterone or norethindrone 5–10 mg daily, or depot MPA 150 mg every 3 months | Reduce bleeding but lower satisfaction |
| Tranexamic acid | 1.5 g orally every 8 hours for 5 days during menses | 26–54%; non-hormonal, suitable when trying to conceive |
| NSAIDs | Mefenamic acid 500 mg three times daily, ibuprofen or naproxen | 10–52% |
How tranexamic acid works. It is a synthetic lysine analogue that reversibly and competitively blocks the lysine-binding sites on plasminogen, so plasmin cannot bind to and break down fibrin — an antifibrinolytic effect that reduces menstrual blood loss without hormones.
If the LNG-IUS is declined or unsuitable, NICE lists tranexamic acid or NSAIDs (non-hormonal) and combined hormonal contraception or cyclical oral progestogens (hormonal). For fibroids of 3 cm or more, refer for further assessment and offer tranexamic acid and/or NSAIDs while investigations are organised. GnRH agonists or antagonists shrink fibroids and reduce bleeding but need add-back therapy to protect bone.
How is acute heavy uterine bleeding managed?
- Admit if haemodynamically unstable, or with bleeding refractory to 24 hours of outpatient treatment — for example soaking more than one pad an hour, haemoglobin under 8 g/dL or signs of hypovolaemia.
- Mechanical tamponade with an intrauterine balloon, Foley catheter or gauze packing for unstable patients.
- High-dose hormones — IV conjugated oestrogen 25 mg every 4–6 hours for 24 hours, or a 35 µg combined pill three times daily for 7 days, if oestrogen is not contraindicated; or high-dose progestins (medroxyprogesterone or norethindrone 20 mg three times daily for 7 days).
- Tranexamic acid — 10 mg/kg IV (up to 600 mg per dose) or 1.5 g orally every 8 hours for 5 days; NSAIDs as adjuncts.
- Procedures if medical treatment fails — dilatation and curettage, uterine artery embolisation or hysterectomy.
What is the cause-specific and surgical treatment of AUB?
| Cause | Treatment (StatPearls) |
|---|---|
| Polyp | Surgical resection |
| Adenomyosis | Hysterectomy is the primary treatment; adenomyomectomy rarely |
| Leiomyoma | Medical (LNG-IUS, GnRH analogues, progestins, tranexamic acid, NSAIDs) or surgical (myomectomy, uterine artery embolisation, endometrial ablation, hysterectomy) depending on fertility wishes and cavity distortion |
| Malignancy / hyperplasia | Surgery with or without adjuvant therapy; high-dose progestins if surgery is not feasible |
| Coagulopathy | Tranexamic acid or desmopressin (for example in von Willebrand disease) |
| Ovulatory dysfunction | Treat the cause — weight loss in PCOS, cabergoline for hyperprolactinaemia, levothyroxine for hypothyroidism |
| Iatrogenic | Reassure for early breakthrough bleeding on continuous pills; review or change the drug |
| Not otherwise classified | Antibiotics for endometritis; embolisation for arteriovenous malformation |
- Hysterectomy — definitive, with high satisfaction; often chosen for adenomyosis when fertility is not wanted.
- Endometrial ablation — alternative to hysterectomy with outcomes similar to the LNG-IUS; not for women who want future pregnancy.
- Myomectomy (hysteroscopic or laparoscopic) — removes fibroids and keeps the uterus; NICE suggests hysteroscopic removal for submucosal fibroids.
- Uterine artery embolisation — mainly for fibroid-related bleeding.
- Dilatation and curettage — an option especially when clots are seen in the cavity; avoid in bleeding disorders.