What is Abnormal Uterine Bleeding?
Abnormal Uterine Bleeding (AUB) refers to any variation from normal menstrual patterns, including changes in regularity, frequency, duration, or volume of menstrual flow. It is one of the most common reasons women seek gynecologic care.
Normal menstrual cycles typically occur every 24-38 days, with bleeding lasting 4.5-8 days. Menstrual blood loss greater than 80 mL per cycle is considered heavy, though in practice, the significance of bleeding is best judged by its impact on quality of life.
The PALM-COEIN Classification
The causes of AUB are organized by the internationally recognized PALM-COEIN system:
Structural Causes (PALM)
- P – Polyps: Growths of the uterine lining that may cause irregular or heavy bleeding
- A – Adenomyosis: Growth of endometrial tissue into the muscular wall of the uterus
- L – Leiomyomas (Fibroids): Non-cancerous uterine muscle growths
- M – Malignancy and hyperplasia: Precancerous or cancerous changes in the uterine lining
Non-Structural Causes (COEIN)
- C – Coagulopathy: Bleeding disorders such as von Willebrand disease
- O – Ovulatory dysfunction: Irregular ovulation from hormonal imbalance, PCOS, or thyroid disorders
- E – Endometrial factors: Disorders of the uterine lining itself
- I – Iatrogenic: Medication-related causes including hormonal contraceptives and anticoagulants
- N – Not yet classified: Other causes not fitting the above categories
Evaluation
A thorough evaluation is important to identify the underlying cause:
- Clinical history: Pattern, duration, and volume of bleeding; associated symptoms; medication use
- Physical examination: Including pelvic exam
- Laboratory tests: Blood count, iron studies, coagulation screen, thyroid function, hormonal assessment
- Pelvic ultrasound: To assess the uterus for structural abnormalities
- Endometrial biopsy: To evaluate the uterine lining when age, bleeding pattern, medication response, or risk factors for endometrial disease make sampling appropriate
- Hysteroscopy: Direct visualization of the uterine cavity when indicated
Treatment Options
Treatment depends on the underlying cause, severity, age, and reproductive plans:
Medical Management
- Hormonal therapies: Combined oral contraceptives, progestins, or hormonal IUD (such as Mirena)
- Non-hormonal therapies: Tranexamic acid, NSAIDs
- Treatment of underlying conditions: Thyroid disorders, coagulation abnormalities
Procedural and Surgical Options
- Endometrial ablation: Treatment of the uterine lining to reduce bleeding for appropriately selected patients who do not want future pregnancy. Pregnancy can still occur and may be dangerous, so reliable contraception is needed afterward. Ablation is not appropriate when cancer or a precancer is suspected.
- Hysteroscopic polypectomy or myomectomy: Removal of polyps or submucosal fibroids through the cervix
- Laparoscopic myomectomy: Removal of fibroids while preserving the uterus
- Hysterectomy: Removal of the uterus; the only treatment that permanently stops uterine bleeding, but also the most invasive option and ends the ability to carry a pregnancy
When to Seek Care
Arrange assessment for bleeding between periods, bleeding after menopause, bleeding that is persistently heavy or prolonged, or bleeding that affects daily life. Seek urgent care for bleeding that soaks through a pad or tampon every hour for more than two hours, particularly with dizziness, fainting, chest pain, shortness of breath, severe pain, or possible pregnancy.
Sources
Clinical content updated July 2026. Sources: ACOG: Abnormal Uterine Bleeding and FIGO PALM-COEIN classification.