Abnormal Uterine Bleeding


Abnormal uterine bleeding (AUB) is a broad term describing irregularities in the menstrual cycle involving frequency, regularity, duration, and volume of flow outside of pregnancy. By definition, AUB does not include bleeding from other parts of the female genital tract (e.g., vulva, vagina, cervix, fallopian tubes, ovaries).

Many terms have traditionally been used to describe AUB. General consensus holds that certain terms should be abandoned to avoid confusion: menorrhagia, metrorrhagia, polymenorrhea, hypermenorrhea, oligomenorrhea, and dysfunctional uterine bleeding.


Preferred characterization involves menses frequency, regularity, duration, and volume:

Frequency24-38 days<24 days: frequent
>38 days: infrequent
Regularity*Variation not exceeding 7-9 days
(depending on age)
≤25yo: cycle length variance >9 days
26-41yo: >7 days
≥42yo: >9 days
DurationTypically 4-8 days>8 days: prolonged
No consensus on shortened duration
Volume**5-80 mL (per cycle)>80 mL: heavy
<5 mL: light
Source: StatPearls

*Intermenstrual bleeding refers to AUB that occurs between well-defined cyclical menses. The distinction between bleeding and spotting is based on the patient’s need for menstrual product use (i.e., spotting is bloody discharge that is not sufficient to require sanitary protection).

**Volume of blood loss is challenging to quantify. In general, heavy menstrual bleeding is accepted to be a volume that interferes with the patient’s quality of life.

Patients with a normal volume of menstrual blood loss tend to change pads/tampons at ≥3 hour intervals, use fewer than 21 pads/tampons per cycle, seldom need to change the pad/tampon during the night, have clots less than 1 inch in diameter, and do not have anemia.

Questions that may help quantify blood loss:

  • How often do you change your sanitary pad/tampon during peak flow days?
  • How many pads/tampons do you use over a single menstrual period?
  • Do you need to change the pad/tampon at night?
  • How large are any clots that are passed?
  • Has a medical provider told you that you have anemia?


There are multiple ways to categorize the broad differential underlying AUB. “PALM-COEIN” is an evidence-based mnemonic for nongravid reproductive-age patients (“PALM” refers to structural criteria while “COEI” refers to non-structural causes):

  • Structural:
    • Polyp
    • Adenomyosis
    • Leiomyoma
    • Malignancy/hyperplasia
  • Non-structural:
    • Coagulopathy
    • Ovulatory dysfunction
    • Endometrial disorders
    • Iatrogenic
  • Not otherwise classified

Non-structural causes predominate in adolescents with AUB. In this population, the most common etiology is anovulation (a diagnosis of exclusion) due to immaturity of the hypothalamic-pituitary-ovarian (HPO) axis, which can take up to 3 years after menarche to mature.

Source: Contemporary OB/GYN Journal

The second most common cause of AUB in adolescents is a bleeding disorder. Most women with a bleeding disorder report heavy menstrual bleeding as the most common manifestation of their disorder, and approximately half of adolescent girls with bleeding disorders present with heavy bleeding at menarche.


For patients who are hemodynamically stable, the physical exam should evaluate for systemic illness (e.g., fever, enlarged thyroid gland, bruising, etc.) and hyperandrogenism (e.g., acne, hirsutism, acanthuses nigricans). A pelvic exam is almost always indicated, but may not be possible in sexually inexperienced adolescents.

Ruling out pregnancy is the most important initial test in work-up. Other common tests to perform early on include CBC, TSH, and pelvic US.

Regarding pelvis US, transvaginal is the preferred route to evaluate female reproductive structures. Structural causes of AUB in adolescents are uncommon, and thus US studies are often low yield; when indicated, the transabdominal route may be more appropriate in this population.

Further testing often depends on clinical suspicion for specific etiologies (e.g., bleeding disorders, etc.)

Blog post based on Med-Peds Forum talk by Emily Kruse, PGY3, and Madeleine Ward, PGY4

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