What is Abnormal Uterine Bleeding (AUB)?
Abnormal uterine bleeding (AUB) is bleeding from the uterine corpus that is abnormal in regularity, volume, frequency, or duration occurring in the absence of pregnancy, affecting at least one-third of women during their lifetime. 1
Core Definition
AUB represents any variation from normal menstrual bleeding patterns and encompasses three main presentations 2:
- Heavy menstrual bleeding (HMB): Predictable cyclical bleeding that is excessive in volume
- Intermenstrual bleeding (IMB): Irregular non-cyclical bleeding between periods
- Irregular menstrual bleeding: Abnormal timing or frequency of bleeding episodes
This standardized terminology replaces older, less precise terms such as "dysfunctional uterine bleeding," "irregular menstrual bleeding," and "menorrhagia" that previously caused confusion in clinical practice 3.
PALM-COEIN Classification System
The International Federation of Gynecology and Obstetrics (FIGO) established the PALM-COEIN classification system to systematically categorize AUB causes into structural and nonstructural etiologies. 1
Structural Causes (PALM)
- Polyp
- Adenomyosis
- Leiomyoma (fibroids)
- Malignancy and hyperplasia
These are discrete anatomic entities that can be visualized on imaging or histopathology 1.
Nonstructural Causes (COEIN)
- Coagulopathy
- Ovulatory dysfunction
- Endometrial disorders
- Iatrogenic causes
- Not yet classified
These represent functional or systemic conditions without discrete structural abnormalities 1.
Age-Specific Patterns
Adolescents
Approximately 95% of AUB in adolescents is anovulatory (dysfunctional), though systematic evaluation remains necessary to exclude underlying systemic or oncological diseases, with particular attention to hyperandrogenism suggesting polycystic ovary syndrome 1.
Premenopausal Women
The most common structural causes are polyps, adenomyosis, and leiomyomas, with ovulatory dysfunction being the predominant nonstructural cause 1, 2.
Postmenopausal Women
Endometrial cancer becomes the primary focus of evaluation in postmenopausal women with bleeding. 1 An endometrial thickness ≥5 mm on transvaginal ultrasound generally prompts endometrial tissue sampling, while thickness <4 mm has a nearly 100% negative predictive value for cancer 1.
Clinical Impact
AUB affects approximately 35% or higher of women, significantly impacting quality of life, productivity, and increasing healthcare burden 3, 4. The condition leads to increased healthcare costs and decreased overall well-being, with potential complications including anemia and the need for hysterectomy if diagnosis and treatment are delayed 5, 6.