Abnormal Uterus Size: Risk Factor or Complication?
Abnormal uterus size is a risk factor (structural cause) for AUB, not a complication of it—the enlarged uterus from conditions like fibroids and adenomyosis causes the bleeding, rather than bleeding causing uterine enlargement.
Understanding the Causal Relationship
The evidence clearly establishes that structural uterine abnormalities that alter uterine size are etiologic factors in AUB, not consequences of the bleeding itself:
Fibroids (leiomyomas) and adenomyosis are the most common structural causes of heavy menstrual bleeding (HMB), both of which increase uterine size and directly cause abnormal bleeding through distortion of the endometrial cavity and altered myometrial contractility 1.
The PALM-COEIN classification system categorizes AUB etiologies, with the "P" (polyp), "A" (adenomyosis), "L" (leiomyoma), and "M" (malignancy) representing structural causes that physically alter uterine anatomy before causing bleeding 2, 3.
Submucous uterine leiomyomas are specifically listed as benign pelvic disorders causing abnormal bleeding, indicating the structural abnormality precedes and causes the bleeding symptom 4.
Clinical Implications
The directional relationship matters for diagnostic approach:
When evaluating AUB, pelvic ultrasound serves as the initial imaging modality specifically to identify structural causes like fibroids and adenomyosis that have already enlarged the uterus 1.
Structural causes of uterine bleeding increase with age, meaning the likelihood of finding an enlarged uterus as the causative factor rises in older reproductive-age women 5.
Important Caveat
While abnormal uterine size causes AUB, secondary complications from chronic AUB include anemia and infertility—not further uterine enlargement 2. The uterine pathology remains the primary driver, though chronic bleeding can lead to systemic consequences that affect quality of life 5.