Causes of Infertility: Uterine Fibroids

Causes of Infertility: Uterine Fibroids

The uterus is composed of a thick layer of smooth muscle (myometrium) surrounding thin lining (the endometrium) into which the embryo implants and which serves to protect and nourish a growing pregnancy.  Approximately 20 to 40% of all reproductive age women will develop benign growths of the myometrium, referred to as fibroid tumors (leiomyomata).  These tumors are rarely malignant (see below).  They can be located in the wall of the uterus (intramural), on the outside of the uterus (subserosal), within the uterine cavity (submucosal), on a thin stalk (pedunculated) or a combination of the above.  Estrogen causes them to grow.  African and African American women seem to have a much higher incidence of fibroid tumors than Caucasian women and Asian women have a reduced risk.

Fibroid tumors, even large ones, can occur without producing any symptoms at all. However, they can also cause a variety of symptoms depending on their size, location and their growth rate.  The most common symptoms are heavy cyclical menstrual bleeding (menorrhagia) accompanied by menstrual pain (dysmenorrhea). Sometimes, especially when a fibroid protrudes into the uterine cavity, it can cause erosion of the endometrial lining and produce irregular or more frequent bleeding (menometrorrhagia). Other possible symptoms include pain with deep penetration during intercourse, bladder irritability, rectal pressure, constipation and painful bowel movements (dyschezia).

For the most part, only those fibroids that impinge upon the endometrial cavity (submucosal) affect fertility.  Exceptions include large intramural fibroids that block the openings of the fallopian tubes into the uterus, and where multiple fibroids cause abnormal uterine contraction patterns.  Surgery to treat fibroids can also affect fertility in several ways.  If the endometrial cavity is entered during the surgery, there is a possibility of post operative adhesion formation within the uterine cavity.  Because of bleeding that may occur during a myomectomy, there is a high likelihood of abdominal adhesion formation, which could encase the ovaries and prevent the release of the eggs or block the ends of the fallopian tubes.  For this reason, it is important that only accomplished surgeons who are familiar with techniques to limit blood loss and prevent adhesion formation perform myomectomies on reproductive age women.

In some cases multiple uterine fibroids may so deprive the endometrium of blood flow, that the delivery of estrogen to the uterine lining (endometrium) is curtailed to the point that it cannot become enriched enough to support a pregnancy. This can result in early 1st trimester (prior to the 13th week of pregnancy) miscarriages. Large or multiple fibroids, by impairing the ability of the uterine growth during pregnancy, may precipitate recurrent 2nd trimester (beyond the 13th week) miscarriages and/or trigger the onset of premature labor.

Sizable fibroid tumors are usually easily identified by a simple vaginal examination. However, even the smallest fibroid can be identified by transvaginal ultrasound.  Sometimes it is difficult to tell if a fibroid is impinging on the endometrial cavity.  In such cases, a hysteroscopy (where a telescope-like instrument is inserted through the vagina and into the uterine cavity) is recommended.  Another, less expensive option to distinguish between intramural and submucosal fibroids is a sonohysterogram – where sterile fluid is injected into the uterine cavity, allowing for examination of its contour and the inner configuration of the endometrium.  Magnetic resonance imaging (MRI) can be used to distinguish between fibroid tumors and related conditions that cannot be managed with surgery.  This contrasts with fibroid tumors, which are well defined and are usually easily removed.

The primary treatment of fibroid tumors is surgical removal (myomectomy).  Small, asymptomatic fibroids that do not impinge upon the endometrial cavity will usually not require treatment other than observation and vigilance.  Large fibroids and submucosal fibroids should be removed prior to starting fertility treatments such as in vitro fertilization (IVF) in order to decrease the chance of implantation failure, miscarriage, pregnancy complications and premature labor. Intramural and subserosal fibroids are readily removable by laparoscopic resection or via an abdominal incision.  The former allows for a more rapid convalescence and is ideal for the removal of small and accessible superficial fibroid tumors, while the latter approach is preferred for treating larger and less accessible fibroids.

Careful repair of the uterine wall is essential in order to reduce the subsequent risk of uterine rupture during pregnancy or labor.  This is one of the main arguments against the use of laparoscopic removal of large, multiple, or remotely situated fibroids.  While a laparoscopic myomectomy requires but a few days (at most) for post-operative convalescence, abdominal myomectomy usually requires 6-8 weeks of recovery time. Whenever the uterine cavity is entered (purposefully or inadvertently), it should always be followed up with a “2nd look” hysteroscopy to rule out scar tissue formation – a complication which occurs frequently as a result of the removal of submucosal fibroids.

Uterine polyps (and in some cases, also submucosal fibroids), can often be removed hysteroscopically (through the vagina).  This eliminates the need for abdominal surgery and greatly reduces the recovery time.  Hysteroscopic surgery is only useful if the majority of the fibroid protrudes into the endometrial cavity, ensuring that the tumor defect will not be too large.  This surgery is often done under laparoscopic guidance, to reduce the risk of uterine perforation.  After hysteroscopic surgery, it is often advisable to prescribe cyclical hormonal therapy for a few moths to encourage regeneration of the endometrial lining over the area of the tumor defect and healing of the uterine muscle. A 2nd look hysteroscopy should be performed a few months later in all cases, to rule out scar tissue formation – even if it means delaying or deferring the initiation of definitive fertility treatment.

Estrogen fuels the growth of fibroids but it does not make them appear.  Thus, when a woman enters menopause and stops making female hormones, fibroids tend to shrink in size on their own.  Conditions that mimic menopause can reduce the size of fibroid tumors by 30 to 60%.  The most common of these treatments is with a medication such as Leuprolide acetate (Lupron), which shuts off the hormone signal from a woman’s brain to her ovaries, preventing hormone production.  However, this type of medication can only be taken for a limited period (usually 6 months) and once the medication is stopped the fibroids will usually regain their original size within a few months.  The medication is therefore only a “temporary fix” used mostly to decrease the size of large fibroids in order to make their ultimate surgical removal easier or to help a woman bridge the gap until spontaneous menopause sets in.

A myomectomy carries a small risk of severe, uncontrollable intra-operative bleeding. Moreover, some women are poor candidates for surgery. An alternative to surgery is embolization.  Embolization is a procedure in which small particles are injected into the arteries of the uterus under guidance of x-rays to obstruct the blood supply to the fibroids inducing them to “shrink” and perhaps even disappear.

Embolization is relatively new to the field of gynecology and we are still learning about its potential effects on future fertility. There is concern that in the process of shutting off the blood supply to the uterus, it will permanently reduce endometrial blood flow, which can compromise embryo implantation.  For this reason, we are still cautious about recommending this therapy for women who still wish to conceive and carry a gestation in their uterus.  At present, it seems best suited for symptomatic women who are finished with their childbearing or who are planning to use a gestational surrogate