Uterine fibroids (leiomyomas or myomas) are non-cancerous growths that develop from the muscle tissue of the uterus. They are extremely common, affecting a large percentage of women during their reproductive years, though many remain unaware they have them. Because these growths often appear when a woman is planning a family, their impact on fertility is a significant concern. While fibroids can complicate the process, it is often possible to get pregnant with them, but the outcome depends heavily on specific biological factors.
How Fibroids Impact Conception
The ability of a fibroid to interfere with conception is primarily determined by its location within the uterine wall, rather than its size. Fibroids are classified into three main types, each presenting a different level of risk to fertility. The least concerning are subserosal fibroids, which develop on the outer surface of the uterus and typically do not affect the internal reproductive environment.
The most disruptive are submucosal fibroids, which grow just beneath the inner uterine lining (endometrium) and protrude into the uterine cavity where an embryo would implant. Even small submucosal fibroids can significantly lower pregnancy rates and increase the risk of miscarriage by distorting the cavity’s shape. This distortion interferes with the embryo’s successful attachment and may alter the local blood flow needed for a healthy implantation site.
Intramural fibroids are the most common type, developing within the muscular wall of the uterus itself. If these fibroids are large or expand inward enough to deform the uterine cavity, they can also interfere with implantation, though their impact is less pronounced than submucosal fibroids. Fibroids may also cause mechanical interference by obstructing the entrance to the fallopian tubes or blocking the cervix. Additionally, they may trigger an inflammatory response in the endometrium or affect the uterus’s normal muscular contractions, creating an environment less favorable for a developing embryo.
Risks During Pregnancy
For women who successfully conceive with fibroids, the pregnancy is generally considered higher risk, though many proceed without major complications. A primary concern is an increased risk of miscarriage, particularly in the first and second trimesters, often associated with submucosal fibroids that distort the uterine space. Fibroids can also undergo degeneration, where the growth outgrows its blood supply, leading to localized pain most common during the first or second trimesters.
Later in pregnancy, fibroids may increase the risk of complications affecting delivery. Large fibroids can increase the likelihood of preterm labor or delivery before 37 weeks gestation. Fibroids can also interfere with the placenta’s function, potentially leading to placental abruption, where the placenta separates from the inner wall of the uterus before birth. Furthermore, fibroids located lower in the uterus may block the birth canal or cause the baby to present in an abnormal position, often necessitating a cesarean section delivery.
Treatment Options to Improve Fertility
For women whose fibroids are directly linked to difficulties conceiving, surgical removal (myomectomy) is the primary treatment option to improve fertility outcomes. The specific surgical approach depends on the fibroid’s location and size. Submucosal fibroids, which are the most detrimental to implantation, can often be removed using a hysteroscopic myomectomy, a less invasive procedure performed through the vagina and cervix.
Fibroids located in the uterine muscle (intramural) or on the outer surface (subserosal) typically require laparoscopic or traditional abdominal myomectomy. Removing submucosal fibroids has been shown to improve pregnancy and live birth rates, particularly when no other cause of infertility is found. Hormonal therapies, such as Gonadotropin-releasing hormone (GnRH) agonists, are sometimes used to temporarily shrink fibroids before surgery, but they must be stopped before attempting conception. Treatment is not always necessary, as small, asymptomatic fibroids often require only monitoring, and many women conceive successfully without intervention.