Uterine fibroids (leiomyomas) are common non-cancerous growths that develop from the muscle tissue of the uterus. They affect a large percentage of women during their reproductive years, though many remain unaware they have them because they cause no symptoms. When symptoms occur, they range from heavy menstrual bleeding to pelvic pressure, depending on the fibroid’s location, size, and number. For those planning a family, the central question is whether subserosal fibroids compromise the ability to conceive.
Understanding Uterine Fibroids and Classification
Uterine fibroids are benign tumors composed of smooth muscle cells and fibrous connective tissue. They are classified based on where they grow within the wall of the uterus, a distinction that largely determines their effect on reproductive function. The three primary classifications are submucosal, intramural, and subserosal.
Submucosal fibroids are located just beneath the endometrium, the inner lining of the uterus, and protrude directly into the uterine cavity. Intramural fibroids are the most common type, growing within the muscular wall of the uterus, known as the myometrium.
Subserosal fibroids develop on the outer surface of the uterus, beneath the serosa, which is the smooth, outermost covering. Unlike submucosal fibroids, these growths expand outward into the pelvic cavity, away from the uterine lining where implantation occurs. Sometimes, a subserosal fibroid can grow on a thin stalk, known as a pedunculated subserosal fibroid.
Direct Link Between Subserosal Fibroids and Infertility
The location of subserosal fibroids means they generally do not interfere with the reproductive process, making a direct link to infertility uncommon. Conception requires a viable egg to be fertilized and then for the resulting embryo to successfully implant into the uterine lining. Subserosal fibroids, by growing on the exterior of the uterus, typically leave the uterine cavity and the endometrium completely undisturbed.
Scientific studies comparing pregnancy and live birth rates in women with subserosal fibroids to those without fibroids have found no significant difference in fertility outcomes. Unlike submucosal fibroids, which distort the uterine cavity and are strongly associated with lower implantation rates and increased miscarriage risk, subserosal fibroids do not compromise the environment required for an embryo to attach and grow. Therefore, for the vast majority of patients, a subserosal fibroid is considered an incidental finding and not the cause of infertility.
In rare cases, a subserosal fibroid may indirectly affect fertility if it grows exceptionally large. A massive fibroid could potentially alter the pelvic anatomy enough to compress or obstruct the fallopian tubes, preventing the egg and sperm from meeting. However, most subserosal fibroids do not reach a size that causes this physical obstruction. Furthermore, there is no evidence that surgically removing an asymptomatic subserosal fibroid improves the chances of becoming pregnant.
Secondary Reproductive and Symptomatic Concerns
While subserosal fibroids rarely cause infertility, they can still lead to other problems due to their outward growth and size. The primary issues are related to “bulk-related” symptoms, where the mass of the fibroid presses on nearby organs. These symptoms include a feeling of pelvic pressure or heaviness.
If a subserosal fibroid is located on the front of the uterus, it can press on the bladder, causing frequent urination or a feeling of incomplete emptying. A fibroid on the back of the uterus may press against the rectum, contributing to constipation or discomfort. The severity of these symptoms is directly related to the fibroid’s size and its precise position within the pelvis.
Subserosal fibroids can also present challenges during or after conception. During pregnancy, a fibroid may undergo degeneration, where it outgrows its blood supply, which can cause acute localized pain. Although they do not typically increase the risk of miscarriage, large fibroids can affect fetal positioning or increase the risk of a cesarean section if they obstruct the birth canal.
Diagnosis and Treatment Options
Subserosal fibroids are typically diagnosed during a routine pelvic examination or through imaging tests. The most common diagnostic tool is a transvaginal or transabdominal ultrasound, which uses sound waves to create an image of the uterus and surrounding structures. Magnetic Resonance Imaging (MRI) provides a more detailed map of the fibroid’s exact size and location, particularly when surgical planning is considered.
Management for subserosal fibroids is generally conservative, as treatment is only necessary if they are causing significant symptoms. For women with small, asymptomatic fibroids, “watchful waiting” is usually adopted, involving periodic monitoring with imaging. If symptoms such as pain or pressure are mild, over-the-counter pain relievers may be sufficient.
When symptoms are severe or when the rare fertility impact is confirmed, intervention may be considered. The main surgical option that preserves the uterus is a myomectomy, often performed laparoscopically for subserosal types. Less invasive options like Uterine Fibroid Embolization (UFE) can shrink fibroids by blocking their blood supply, though myomectomy is often preferred for those wishing to preserve fertility.