What is considered abnormal uterine bleeding?

Definition of Abnormal Uterine Bleeding

Abnormal uterine bleeding (AUB) is defined as bleeding from the uterine corpus that is abnormal in regularity, volume, frequency, or duration and occurs in the absence of pregnancy. 1

Core Definition Parameters

AUB represents any deviation from normal menstrual patterns across four key dimensions:

• Regularity: Unpredictable timing of bleeding episodes 1
• Volume: Excessive blood loss during menstruation 1
• Frequency: Bleeding occurring too often or too infrequently 1
• Duration: Bleeding lasting longer than normal (typically >8 days is considered abnormal) 2, 3

Clinical Presentations

AUB encompasses three main bleeding patterns:

• Heavy menstrual bleeding (HMB): Predictable cyclical bleeding that is excessive in volume, often exceeding 8 days duration 3, 4
• Intermenstrual bleeding (IMB): Irregular non-cyclical bleeding between menstrual periods 3
• Combined patterns: Both heavy and prolonged menstrual bleeding occurring together 4

PALM-COEIN Classification System

The International Federation of Gynecology and Obstetrics (FIGO) developed the PALM-COEIN classification system to systematically categorize all causes of AUB in reproductive-age women. 1

Structural Causes (PALM):

• Polyp: Endometrial polyps causing focal bleeding 5, 1
• Adenomyosis: Endometrial tissue within the myometrium 5, 1
• Leiomyoma: Uterine fibroids, the most common structural cause in women under 40 5, 1
• Malignancy and hyperplasia: Endometrial cancer or precancerous changes, the most serious etiology particularly in postmenopausal women 5, 1

Non-Structural Causes (COEIN):

• Coagulopathy: Bleeding disorders affecting hemostasis 5, 1
• Ovulatory dysfunction: Anovulation causing irregular bleeding patterns 5, 1
• Endometrial: Primary endometrial disorders with molecular deficiencies in hemostasis regulation 5, 1
• Iatrogenic: Bleeding from exogenous hormones, intrauterine devices, or anticoagulation therapy (approximately 70% of women on anticoagulation experience this) 5, 1
• Not yet classified: Causes not fitting other categories 5, 1

Age-Specific Considerations

Reproductive-Age Women:

• Most commonly experience AUB from structural causes (polyps, adenomyosis, leiomyomas) and non-structural causes (ovulatory dysfunction, coagulopathies, iatrogenic causes) 1

Perimenopausal Women:

• Anovulation is the most frequent cause, though structural causes must be ruled out 1

Postmenopausal Women:

• Endometrial cancer becomes the primary concern and main focus of evaluation 1

Urgent Evaluation Criteria

Urgent assessment is warranted when bleeding saturates a large pad or tampon hourly for at least 4 consecutive hours, indicating potential hemodynamic instability. 5

Common Pitfall

The outdated terms "dysfunctional uterine bleeding," "menorrhagia," and "irregular menstrual bleeding" have been replaced by the more precise term "abnormal uterine bleeding" with specific descriptors for the bleeding pattern. 4, 6