Uterine fibroids are non-cancerous growths that develop from the muscle tissue of the uterus. They affect between 50% and 80% of women by the time they reach menopause, though many never experience symptoms. While fibroids are benign, their presence can significantly affect a woman’s reproductive health, including her ability to conceive and maintain a pregnancy. The impact on fertility depends on the size, number, and, most importantly, the specific location of the fibroids within the uterus.
Understanding Fibroid Types and Location
Fibroids are classified according to where they are situated relative to the uterine wall, which dictates their potential to interfere with conception. The most problematic type for fertility are submucosal fibroids, which grow directly beneath the uterine lining and protrude into the uterine cavity. Even small submucosal fibroids can dramatically reduce the chance of a successful pregnancy because they directly disrupt the area where an embryo must implant.
Intramural fibroids are the most common type, developing within the muscular wall of the uterus itself. Their effect on fertility is variable and largely depends on their size; larger intramural fibroids, particularly those over six centimeters, can impair conception outcomes.
The third main type, subserosal fibroids, grow on the outer surface of the uterus and protrude into the pelvic cavity. These are considered to have the least effect on fertility outcomes because they do not interfere with the uterine cavity or the fallopian tubes. Their removal is typically not recommended solely for the purpose of improving conception chances.
Mechanisms of Impaired Conception and Implantation
Fibroids interfere with the reproductive process through a combination of physical and biochemical alterations to the uterine environment. The most direct impact comes from the mechanical distortion of the uterine cavity, often caused by submucosal fibroids, which can physically block sperm from reaching the egg or impede the fertilized egg’s journey. This distortion also prevents the necessary close alignment between the developing embryo and the uterine lining, hindering successful implantation.
Beyond physical obstruction, fibroids can create a hostile environment through changes in blood flow and inflammation. Large fibroids may compress nearby arteries, disrupting the blood supply to the endometrium. This compromised blood flow also contributes to a localized state of chronic inflammation within the uterine lining.
This inflammatory environment and altered blood supply trigger molecular changes in the endometrium that reduce its receptivity to an embryo. Fibroids can alter the expression of specific genes and growth factors necessary for the uterine lining to mature and allow implantation. Fibroids can also interfere with the normal muscular contractions of the uterus, known as peristalsis, which are necessary for the transport of sperm and the embryo, further disrupting the process of conception.
Treatment Options for Fertility Preservation
When fibroids are identified as the cause of infertility, the primary course of action to restore fertility is surgical removal via a procedure called myomectomy. The specific surgical approach depends entirely on the fibroid’s location; submucosal fibroids are typically removed through a hysteroscopic myomectomy, where instruments are passed through the vagina and cervix, offering a minimally invasive option. For intramural or subserosal fibroids, an abdominal myomectomy, which can be open or laparoscopic, is often required to access the growths within the uterine wall.
Medical management, such as the use of Gonadotropin-Releasing Hormone (GnRH) agonists, is sometimes employed. These medications temporarily induce a menopause-like state, causing fibroids to shrink by reducing the production of estrogen. They are most often used for a short duration before a planned myomectomy to reduce the size of large fibroids and decrease surgical blood loss.
Another treatment is Uterine Fibroid Embolization (UFE), a procedure that blocks the blood supply to the fibroids, causing them to shrink. While UFE is a less invasive alternative to surgery, it is generally not the preferred choice for women who are actively trying to conceive. Reproductive outcomes are considered superior following a myomectomy compared to UFE, which may carry a risk of compromising ovarian function or placental development.