Uterine fibroids (leiomyomas) are non-cancerous growths that develop from the muscle tissue of the uterus. These tumors are extremely common, affecting many women during their reproductive years, though many remain unaware of their presence. While fibroids can cause pelvic pain or pressure, they are a frequent cause of abnormal uterine bleeding (AUB), often manifesting as heavy or prolonged menstrual periods. Symptomatic fibroids, especially those causing bleeding, are a leading reason for seeking gynecological care.
Types of Fibroids and Bleeding Risk
The location of a fibroid within the uterine wall is the greatest determinant of its potential to cause excessive bleeding. Fibroids are classified into three main types based on where they grow relative to the uterine layers, and each type presents a distinct risk profile for abnormal flow.
Submucosal fibroids push into and distort the uterine cavity, posing the highest risk for heavy menstrual bleeding and spotting. Even small submucosal fibroids cause significant disruption because they directly interfere with the endometrium, the lining that sheds during menstruation.
Intramural fibroids grow entirely within the muscular wall of the uterus (myometrium). They may cause bleeding if they become large or numerous enough to stretch the cavity or impair muscle function.
Subserosal fibroids are located on the outer surface of the uterus, often projecting outward toward the pelvic cavity. Because this type does not affect the uterine lining or muscular contractions, they rarely cause heavy or prolonged menstrual bleeding. Instead, subserosal fibroids are more likely to cause symptoms related to bulk, such as pelvic pressure, frequent urination, or pain, due to pressing on nearby organs.
Physical Mechanisms of Excessive Bleeding
Fibroids, especially those near the uterine cavity, trigger heavy or prolonged bleeding through multiple mechanisms. One major factor is the distortion of the uterine cavity, which significantly increases the surface area of the endometrial lining available to shed each month. This increased volume of tissue results in a heavier menstrual flow than a normal cycle.
The presence of fibroids within the myometrium also interferes with the uterus’s natural ability to stop bleeding after the lining has shed. Normally, the muscular wall contracts strongly to clamp down on blood vessels, a process called hemostasis. Fibroids disrupt the organized muscle fiber structure, impairing these contractions and preventing effective constriction, which leads to prolonged flow.
Fibroids also generate an irregular and fragile network of blood vessels, known as aberrant angiogenesis. This rich, abnormal blood supply, sometimes referred to as a pseudocapsule, is prone to leakage and poor regulation. This increased vascularity contributes to heavier blood flow and can lead to fragile vessels that are more likely to rupture during the menstrual cycle.
Secondary Effects of Prolonged Bleeding
The chronic and excessive blood loss associated with fibroids can lead to systemic health problems. The most common secondary effect is iron deficiency anemia, resulting from the body’s inability to replace red blood cells lost during heavy periods. This condition develops when the body’s iron stores are depleted, which are needed to produce hemoglobin, the protein that carries oxygen in red blood cells.
Anemia leads to persistent symptoms that significantly reduce quality of life. Common complaints include overwhelming fatigue, weakness, dizziness, and shortness of breath, even during light activity. The need to manage heavy flow, combined with the physical symptoms of anemia, can disrupt work, social activities, and emotional well-being.
Initial Approaches to Managing Bleeding
Initial treatment strategies focus on controlling the heavy flow symptom, often without immediately addressing the fibroids themselves. Medical management frequently involves hormonal therapies to regulate the menstrual cycle and reduce bleeding volume.
Hormonal and Non-Hormonal Medications
Hormonal options include oral contraceptive pills, which thin the endometrial lining, and the levonorgestrel-releasing intrauterine device (LNG-IUD). The LNG-IUD releases a progestin directly into the uterus to suppress endometrial growth. Non-hormonal medications are also used, such as tranexamic acid, which promotes blood clotting to reduce blood loss. NSAIDs can also reduce blood flow by influencing prostaglandin production.
Targeted Procedures
For more targeted intervention, procedures are available that aim to reduce bleeding while preserving the uterus. Hysteroscopic myomectomy is a minimally invasive procedure preferred for removing submucosal fibroids, as it addresses the fibroid directly. Uterine artery embolization (UAE) is another option; it blocks the blood vessels feeding the fibroids, causing them to shrink and significantly reducing the heavy flow.