Uterine fibroids affect up to 80 percent of women by age 50, yet their impact on fertility remains widely misunderstood. While many women with fibroids conceive without difficulty, certain types and locations of these benign tumors can significantly reduce fertility and complicate pregnancy outcomes.
The path to parenthood often includes unexpected obstacles, but few are as common yet misunderstood as uterine fibroids. These non-cancerous growths of muscle tissue within and around the uterus affect a remarkable percentage of reproductive-age women, with Black women experiencing them at nearly three times the rate of white women and often developing them at younger ages.
Location matters more than size
The first crucial factor in how fibroids affect fertility is their specific location within the reproductive system. Research from fertility centers consistently shows that not all fibroids impact conception equally.
Submucosal fibroids, which develop under the uterine lining and protrude into the uterine cavity, cause the most significant fertility challenges. Even small growths in this location can prevent embryo implantation or increase the risk of early miscarriage by distorting the endometrial cavity where an embryo would normally attach and develop.
Intramural fibroids, which grow within the muscular walls of the uterus, present a more complicated picture. Those that distort the uterine cavity appear to reduce fertility, while those that don’t affect the cavity have less impact. Size becomes relevant primarily when these fibroids grow large enough to alter the shape of reproductive structures.
Subserosal fibroids, which develop on the outer surface of the uterus, generally don’t impact fertility unless they grow large enough to compress the fallopian tubes or significantly distort the overall anatomy of the reproductive system.
Implantation interference through multiple mechanisms
The second way fibroids impact fertility involves embryo implantation. For pregnancy to occur, a fertilized egg must successfully implant in the uterine lining, a process requiring precise hormonal and structural conditions.
Fibroids can alter blood flow to the endometrium, potentially creating areas with insufficient vascular supply for supporting early pregnancy. Research indicates fibroids may affect the expression of multiple genes involved in implantation, including those regulating attachment proteins, growth factors and immune response modulators.
Inflammatory processes appear particularly important, as fibroids can trigger local inflammation that creates an environment less hospitable to implantation. Studies have found altered levels of inflammatory cytokines in the uterine environment of women with fibroids, potentially creating conditions that reject rather than welcome an embryo.
Obstruction of reproductive passages
The third fertility impact involves physical obstruction. Fibroids in certain locations can block the fallopian tubes or cervix, preventing the normal movement of eggs, sperm or embryos through the reproductive tract.
Large fibroids near the cornua, where the fallopian tubes connect to the uterus, may prevent sperm from reaching an egg or stop a fertilized egg from traveling to the uterus. This obstruction can increase the risk of ectopic pregnancy, a potentially dangerous condition where the embryo implants outside the uterus, most commonly within a fallopian tube.
Fibroids near the cervix can block sperm entry into the uterus or interfere with procedures like intrauterine insemination or embryo transfer during fertility treatments, requiring additional interventions to navigate around these obstacles.
Hormonal disruption affecting ovulation and uterine environment
The fourth mechanism involves hormonal factors. While fibroids primarily respond to hormones rather than produce them, they can create secondary hormonal effects that impact fertility.
Research suggests fibroids may alter the production of certain peptides and growth factors within the uterine environment. These substances play important roles in regulating implantation and early pregnancy development. The endometrium adjacent to fibroids sometimes shows altered receptor expression, potentially changing how these tissues respond to normal hormonal signals.
Some evidence indicates women with significant fibroid disease may experience subtle alterations in normal ovulatory patterns, though this connection requires further research. The relationship appears bidirectional, hormonal fluctuations affect fibroid growth, while fibroids may subtly influence hormonal function.
Pregnancy complications despite successful conception
The fifth impact extends beyond conception to pregnancy outcomes. Women with fibroids who do become pregnant face higher risks of complications that can affect both maternal and fetal health.
Miscarriage rates increase by approximately 15 percent among pregnant women with submucosal fibroids compared to those without fibroids. The risk appears directly related to fibroid location and the degree of cavity distortion.
During later pregnancy, fibroids can contribute to preterm delivery, abnormal fetal positioning, placental abruption and cesarean delivery. As pregnancy progresses and the uterus expands, fibroids can outgrow their blood supply, causing a painful condition called red degeneration.
Fibroid may also restrict fetal growth in some cases, particularly when they’re large or located near the placental implantation site. They can compete with the developing fetus for blood supply or prevent normal uterine expansion as pregnancy advances.
Despite these potential complications, it’s important to recognize that most women with fibroids can and do have successful pregnancies. The impact depends heavily on individual factors including the number, size, location and growth patterns of the fibroids.
Medical management options have expanded significantly in recent years. For women experiencing fertility challenges related to fibroids, treatments range from hormonal therapies to minimally invasive procedures like uterine artery embolization, focused ultrasound surgery, and myomectomy, the surgical removal of fibroids while preserving the uterus.
The appropriate approach depends on multiple factors including the woman’s age, fertility goals, fibroid characteristics and other aspects of reproductive health. A reproductive endocrinologist can provide personalized guidance about which treatments might offer the best balance of fertility preservation and symptom relief.
Recent research has also identified promising molecular targets that may eventually lead to medications specifically designed to shrink fibroids without affecting other reproductive functions, potentially offering less invasive options for women hoping to preserve or enhance fertility.
For women with known fibroids who are contemplating pregnancy, preconception consultation with both a gynecologist and reproductive specialist can help identify potential challenges and develop strategies to maximize the chances of successful conception and healthy pregnancy.
