What causes bleeding in a premenopausal woman with a uterine myoma (fibroid)?

Mechanism of Bleeding in Uterine Myomas

Bleeding in premenopausal women with uterine myomas occurs primarily through mechanical distortion of the endometrial cavity, increased endometrial surface area, impaired endometrial blood supply leading to venous congestion and ulceration, and disruption of normal uterine contractility that prevents hemostasis. 1

Primary Pathophysiologic Mechanisms

Submucosal Fibroids: The Dominant Bleeding Source

Submucosal myomas are the most significant cause of abnormal uterine bleeding because they directly distort the endometrial cavity and increase the surface area available for menstrual shedding. 2 The bleeding mechanism involves:

• Direct mechanical distortion of the endometrial cavity that prevents normal hemostatic mechanisms 1
• Increased endometrial surface area requiring more blood flow and creating larger areas for menstrual shedding 2
• Atrophy and ulceration of the overlying endometrium due to impaired blood supply 1
• Impaired uterine contractility that normally compresses spiral arterioles to achieve hemostasis after menstruation 2

Intramural Fibroids with Cavity Encroachment

Intramural myomas that encroach into the uterine cavity cause bleeding through similar mechanisms as submucosal fibroids, even without frank cavity distortion. 2 These fibroids:

• Compress and distort the endometrial-myometrial interface 1
• Impair venous drainage leading to endometrial congestion 1
• Disrupt normal endometrial blood flow patterns causing irregular bleeding 2

Subserosal Fibroids: Minimal Bleeding Impact

Subserosal fibroids typically do not cause abnormal uterine bleeding because they project outward from the uterine serosa without affecting the endometrial cavity. 1 The evidence demonstrates:

• Pregnancy and implantation rates are not influenced by subserosal fibroids 1
• These fibroids cause bulk symptoms rather than bleeding 1

Location-Specific Bleeding Risk

The relationship between fibroid location and bleeding severity follows a clear hierarchy: submucosal > intramural with cavity distortion > intramural without cavity distortion > subserosal. 1, 2

Critical Clinical Correlation

• Submucosal fibroids are associated with the most severe menorrhagia requiring intervention 2
• Intramural fibroids cause bleeding primarily when they encroach on the endometrial cavity 2
• Subserosal fibroids rarely cause bleeding as an isolated symptom 1

Secondary Contributing Factors

Vascular Alterations

• Increased vascularity in the fibroid pseudocapsule and surrounding myometrium 3
• Venous ectasia and congestion in the endometrium overlying fibroids 1
• Impaired vasoconstriction of spiral arterioles due to mechanical disruption 2

Endometrial Dysfunction

• Impaired gamete transport and endometrial receptivity changes 1
• Atrophic changes in endometrium overlying submucosal fibroids 1
• Ulceration of the endometrial surface in severe cases 1

Clinical Implications for Treatment Selection

Understanding the bleeding mechanism guides treatment choice: hysteroscopic myomectomy for submucosal fibroids provides the most direct resolution of bleeding by removing the mechanical distortion. 1, 4

Treatment Algorithm Based on Bleeding Mechanism

• Submucosal fibroids <5 cm: Hysteroscopic myomectomy is the procedure of choice with equivalent symptom improvement to more invasive approaches 1
• Intramural fibroids with cavity encroachment: Abdominal or laparoscopic myomectomy provides good bleeding control 2
• Medical management targets: NSAIDs reduce prostaglandin-mediated bleeding, tranexamic acid stabilizes clot formation, and hormonal therapies reduce endometrial proliferation 1, 5

Common Pitfall to Avoid

Do not assume all fibroids cause bleeding—subserosal fibroids rarely require treatment for bleeding alone, and unnecessary intervention should be avoided. 1 Focus treatment on fibroids with documented cavity distortion or submucosal location when bleeding is the primary symptom.