Uterine fibroids are non-cancerous growths that develop within the muscular wall of the uterus. These common growths affect a significant number of women during their reproductive years, with prevalence rates ranging from approximately 35% to 80%, depending on factors like age and ethnicity. While many women with fibroids experience no symptoms, their presence can sometimes impact a woman’s ability to conceive and carry a pregnancy.
How Fibroids Can Influence Fertility
Uterine fibroids can interfere with fertility through several mechanisms, primarily by altering the uterine environment necessary for conception and implantation. They can distort the uterine cavity, making it challenging for an embryo to implant successfully by altering the uterus’s shape and size.
Fibroids may also physically obstruct the fallopian tubes, preventing the egg and sperm from meeting or hindering the passage of a fertilized egg into the uterus. Changes in the shape of the cervix caused by fibroids can affect the number and movement of sperm entering the uterus, further impeding fertilization.
The presence of fibroids can alter blood flow to the uterine lining, known as the endometrium. Reduced or abnormal blood supply can diminish nutrients and oxygen to a developing embryo, potentially affecting its ability to implant and grow. Fibroids can also interfere with the normal rhythmic contractions of the uterus, important for embryo transport and implantation, potentially leading to implantation failure or increased miscarriage risk.
Beyond physical and circulatory changes, fibroids may induce molecular and hormonal alterations within the uterine environment. They can disrupt the expression of genes involved in endometrial receptivity. These molecular disruptions can create an inflammatory response or alter the local hormonal balance, making the uterine lining less receptive to embryo implantation.
Specific Fibroid Types and Their Effects
The impact of fibroids on fertility often depends on their location within the uterus.
Submucosal Fibroids
Submucosal fibroids grow just beneath the uterine lining and protrude into the uterine cavity. They have the most significant effect on fertility, directly distorting the uterine cavity, making successful embryo implantation more difficult and increasing the risk of miscarriage. Their removal has been shown to improve pregnancy rates.
Intramural Fibroids
Intramural fibroids are located within the muscular wall of the uterus. Their influence on fertility varies, largely depending on their size and whether they significantly distort the uterine cavity. Large intramural fibroids (5 centimeters or larger, or those that compromise the uterine cavity) may reduce fertility and increase the chance of pregnancy loss. However, the decision to remove intramural fibroids for fertility purposes is often individualized, as the benefits can be less clear compared to submucosal fibroids.
Subserosal Fibroids
Subserosal fibroids grow on the outer surface of the uterus. These fibroids typically have the least impact on fertility because they do not usually affect the uterine cavity or fallopian tubes. Unless they grow to a very large size and press on nearby organs, their presence is generally not considered a cause of infertility. Removing subserosal fibroids usually does not improve fertility outcomes.
Managing Fibroids When Trying to Conceive
For individuals with fibroids who are trying to conceive, a thorough evaluation is the first step to determine their potential impact.
Diagnosis
Diagnostic methods often include transvaginal ultrasound and magnetic resonance imaging (MRI) to map the size, number, and location of fibroids. For a more detailed view of the uterine cavity, procedures like hysteroscopy or saline infusion sonography (SIS) may be performed.
Myomectomy
Myomectomy is a surgical procedure to remove fibroids while preserving the uterus, making it a preferred option for women desiring pregnancy. The approach varies based on fibroid location: hysteroscopic myomectomy is used for submucosal fibroids, while laparoscopic or open abdominal surgery is typically used for intramural and subserosal fibroids. While hysteroscopic removal does not traumatize the uterine wall, abdominal or laparoscopic myomectomies might necessitate a Cesarean section for future deliveries.
Medications
Medications are generally used to manage fibroid symptoms, such as heavy bleeding and pain, and can temporarily shrink fibroids. However, treatments like gonadotropin-releasing hormone (GnRH) agonists, progestins, or birth control pills are not typically long-term solutions for fertility issues caused by fibroids, as fibroids often regrow after discontinuing medication.
Procedures Not Recommended for Fertility Preservation
Certain procedures are generally not recommended for women who wish to preserve their fertility. Uterine artery embolization (UAE), which blocks blood flow to fibroids, can impact the uterus and is usually not advised for those seeking pregnancy. Similarly, endometrial ablation, a procedure that destroys the uterine lining to reduce heavy bleeding, significantly reduces fertility and increases the risk of serious pregnancy complications, making it unsuitable for women planning to conceive. Consulting with a fertility specialist or a gynecologist experienced in fibroid management is important to determine the most appropriate course of action based on individual circumstances and reproductive goals.