How Uterine Fibroids Causes Infertility in Women

The uterus is composed of a thick layer of smooth muscle (myometrium) surrounding a thin lining (the endometrium) into which the embryo implants and which serves to protect and nourish a growing pregnancy. It is the thin endometrium which is shed each month during the menstruation, if pregnancy does not occur. Some have stated that it is as though the uterus “weeps tears of blood in mourning for the fact that conception did not take place in the cycle. In other words, all hormonal events of the menstrual cycle, have a single purpose in mind – namely successful conception.

Approximately 20-40% 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 any combination of the above. They are hormone dependent lesions and estrogen causes them to grow. African and African American women seem to have a much higher incidence of fibroid tumors. This is indicative of the fact that their cause has a fundamental genetic basis.
Most fibroids start as very small lesions (sometimes referred to as “seedling fibroids”) and they can grow to very large sized lesions. Fibroids as big as watermelons have been reported in the literature. The impact of fibroid tumors on successful reproduction, have a lot to do with location (see below).

Presentation, Symptoms and Signs associated with Uterine Fibroids

Fibroid tumors, even large ones, can occur without producing any symptoms at all (asymptomatic). However they can also cause a variety of symptoms depending on their size, location and the absence or presence of complications such as tortion (twisting) or degeneration (such as might occur when a fibroid grows so fast that it starts running out of its blood supply). 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 continuous bleeding (menomettrorhagia).Sustained non-menstrual pelvic pain may point to tortion of a pedunculated fibroid that is attached to the inner or outer wall of the uterus, or to degeneration, Other possible symptoms include pain with deep penetration during intercourse (deep dyspareunia), bladder irritability, rectal pressure, constipation and painful bowel movements (dyschezia). If a fibroid undergoes degeneration, it can become secondarily infected and in addition to pain, the patient may have fever and chills.

Effect of Fibroids on Reproduction

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. Another lesion that can cause significant problems is the one that grows off the back side of the uterus and occupies to a greater or lesser degree, the cui de sac (area behind the uterus). This location is very important in the physiology of conception, therefore it is not uncommon to see patients with these kinds of lesions present with infertility. 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. This should always be checked for through the performance of a hysteroscopy or fluid ultrasound prior to beginning fertility treatment. Because myomectomy can be bloody, there is a high likelihood of abdominal adhesion formation, which could encase the ovaries, preventing the release of the eggs or block the ends of the fallopian tubes, or otherwise interfere with the normal functioning and relationships of the pelvic organs. For this reason it is important that only accomplished surgeons, who are familiar with techniques to limit blood loss and prevent adhesion foundation, perform myomectomies.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 thicken 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 curtailing the ability of the uterus to stretch in order to accommodate the spatial needs of a rapidly growing pregnancy, may precipitate recurrent 2nd trimester (beyond the 131h week) miscarriages and/or trigger the onset of premature labor. As stated above, the location of the lesions is very important in the symptoms/impact. A lesion positioned just beneath the endometrial lining can make the structural integrity of the endometrium quite unstable and the therefore, unable to develop in a progressive manner in preparation for implantation of the embryo.

Diagnosis

Sizable fibroid tumors are usually easily identified by simple bi-manual 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 via the vagina into the uterine cavity) or a hysterosonogram (where injected t1uid, distends the uterine cavity allowing for examination of its contour and inner configuration) can help distinguish between intramural and submucosal. Magnetic Resonance Imaging (MRI) can be used to distinguish between fibroid tumors and a related condition called adenomyosis, in which diffuse or localized foci of endometrial tissue can be found within the myometrium. Given the often-diffuse nature of adenomyosis, it is difficult to remove surgically. This contrasts with fibroid tumors, which are well defined and are usually relatively easily removed at surgery.