Abnormal Uterine Bleeding

Abnormal uterine bleeding (AUB) is a broad term that describes irregularities in the menstrual cycle involving the parameters of frequency, regularity, duration, and volume of flow outside of pregnancy in reproductive-aged women. (Please see StatPearls' companion resources, "Postmenopausal Bleeding," for more information on diagnosis and management in postmenopausal women). Up to one-third of women will experience AUB in their life, with irregularities most commonly occurring at menarche and perimenopause. A normal menstrual cycle has a frequency of 24 to 38 days and lasts 2 to 7 days, with 5 to 80 mL of blood loss. Therefore, variations in any of these 4 parameters constitute AUB. AUB terminology and classification have evolved to promote clarity and uniformity in diagnosis. Revisions to AUB terminology were first published in 2007, followed by updates from the International Federation of Obstetrics and Gynecology (FIGO) in 2011 and 2018. In 2007, FIGO System 1 established more defined descriptive terms nongestational AUB based on the frequency, regularity, duration, and volume of flow. The nonspecific terminology of menorrhagia, metrorrhagia, and oligomenorrhea was also replaced with the terms heavy menstrual bleeding (HMB) characterized by bleeding >80 mL or heavy enough to interfere with a patient's qualify of life, intermenstrual bleeding (ie, cyclical or random spontaneous bleeding between menstrual periods) and breakthrough bleeding (BTB) on hormone medication. (Please refer to the  section for more information on AUB descriptions). FIGO System 2 introduced PALM-COEIN, which categorizes AUB into structural (polyp, adenomyosis, leiomyoma, malignancy/hyperplasia) and nonstructural (coagulopathy, ovulatory dysfunction, endometrial, iatrogenic, not otherwise classified) etiologies. The committee also defined irregular bleeding as any bleeding that falls outside the 5th to 95th percentiles for any menstrual parameter (eg, regularity, frequency, duration, and volume). AUB can also be divided into acute and chronic bleeding. Acute AUB is excessive bleeding that requires immediate intervention to prevent further blood loss. Acute AUB can occur on its own or superimposed on chronic AUB, which refers to irregularities in menstrual bleeding for most of the previous 6 months. Understanding acute versus chronic AUB helps clinicians tailor evaluation and management strategies, ensuring optimal patient outcomes. Evaluation involves a detailed history, physical examination, laboratory tests, and diagnostic imaging or endometrial sampling when indicated. Management approaches primarily treat the underlying etiology and optimize bleeding with strategies individualized based on AUB severity, cause, and patient preference.