Uterine fibroids, also known as leiomyomata or myomas, are benign (noncancerous) smooth muscle tumors that are commonly found in the uterine wall (Pic. 1). Although the majority of women develop myomas during their fertile period, medical treatment is required only in a minority of cases, when the myomas present with symptoms affecting the quality of life.

Uterine fibroids are the most common solid tumors of the female genital tract. They arise from undifferentiated (mesenchymal) cells in the uterine body and imitate the muscular and connective tissue of the uterine wall. Typically, fibroids appear as well-defined, solid masses with a whorled appearance (Pic. 2). Despite the fact that their cause is still unknown, there is considerable evidence that estrogens (the primary female sex hormones) and progestogene (sex hormone released in the second half of the menstrual cycle) promote their growth, as the fibroids rarely appear before menarche and regress after menopause.

Growth and location are the main factors that determine if a fibroid leads to symptoms and problems. A small lesion can be symptomatic if located within the uterine cavity while a large lesion on the outside of the uterus may go unnoticed. Fibroids may be single or multiple. Most fibroids start in the muscular wall of the uterus. With further growth, some lesions may develop towards the outside of the uterus or towards the internal cavity.

Different locations (Pic. 3) are classified as follows:

  • Intramural fibroids are located within the muscular wall of the uterus and are the most common type. Unless they are large, they may be asymptomatic. Intramural fibroids begin as small nodules in the muscular wall of the uterus. With time, intramural fibroids may expand inwards, causing distortion and elongation of the uterine cavity.
  • Subserosal fibroids are located on the surface of the uterus. They can also grow outward from the surface and remain attached by a small piece of tissue and then are called pedunculated fibroids (located on a thin “stalk”). These pedunculated growths can actually detach from the uterus to become a parasitic leiomyoma (a leiomyoma completely separated from the uterus).
  • Submucosal fibroids are located in the muscle beneath the endometrium of the uterus and distort the uterine cavity; even small lesions in this location may lead to bleeding and infertility. A pedunculated lesion within the cavity is termed an intracavitary fibroid and can be passed through the cervix.
  • Cervical fibroids are located in the wall of the cervix (neck of the uterus). Rarely, fibroids are found in the supporting structures (round ligament, broad ligament, or uterosacral ligament) of the uterus that also contain smooth muscle tissue.

Secondary changes that may develop within fibroids are hemorrhage (bleeding into the tumour), necrosis (tissue death inside the tumour), calcification, and cystic changes (development of a hollow space inside the tumour). They tend to calcify after menopause. If the uterus contains too many to count, it is referred to as diffuse uterine leiomyomatosis.

Treatment options

Therapeutic options to treat these symptoms include medical therapy, surgical interventions and uterine artery embolization (artificial clotting of the artery). Medical treatments used to manage bleeding symptoms are oral contraceptives or progestins, although there is no evidence for their efficacy in treating myomas. Other medical alternatives are the Levonorgestrel-releasing intrauterine system (LNG-IUS) and GnRH-agonists (drugs mimicking the action of gonadotropin-releasing hormone). However, the LNG-IUS cannot be applied in case of significant distortion of the uterine cavity and the duration of treatment with GnRH-agonists is limited by the induction of hypoestrogenic symptoms. According to the reproductive desire of the patient and the severity of symptoms surgical procedures comprise myomectomy (surgical excision of the tumours), endometrial ablation (removal of the inner uterine lining) or hysterectomy (surgical removal of the uterus).

Symptoms

The majority of women with uterine fibroids are asymptomatic, consequently get less clinical attention and fibroid tumours often remain undiagnosed. Symptomatic women typically complain about abnormal uterine bleeding, specifically in terms of heavy and prolonged bleeding. Additionally, women with uterine fibroids may suffer more often from dyspareunia (painful sexual intercourse) and non-cyclic pelvic pain. Large, cavity-distorting tumors are often implicated in iron-deficiency anemia (secondary to abnormal uterine bleeding) and infertility. Tumors in other locations, namely, intramural (well separated from the uterine cavity) and subserosal subtypes, are more often associated with pelvic pressure, pelvic pain, dyspareunia, chronic constipation, and urinary incontinence.

Associated diseases

  • pelvic pain
  • dyspareunia
  • abnormal uterine bleeding
Complications 

Adverse pregnancy outcomes

If a given patient is able to achieve pregnancy with a leiomyoma impacting the uterine cavity, they also are more likely to experience adverse pregnancy outcomes to include recurrent pregnancy loss (RPL), abnormal placentation (abnormal localizations of the placenta), fetal malpresentation, preterm delivery, cesarean section, and postpartum hemorrhage (significant hemorrhage following childbirth).

Abnormal bleeding

In women with large, mainly intramural fibroids, menstrual bleeding tends to be abnormally heavy and prolonged, due to a mechanical obstacle in the uterine wall that prevents the muscular wall from contracting properly to reduce the bleeding. Some women may even develop severe anemia due to excessive blood loss.

Risk factors

Risk factors for the development of the disease have been identified and include increasing age, nulliparity (having never given birth), obesity, premenopausal status, personal history of hypertension (high blood pressure), family history, race/ethnicity, time since last birth, and consumption of food additives and soybean milk. 

Of note, the strongest epidemiologic correlate is increasing age followed by a woman’s race/ethnic background. To this end, women of African descent are at increased risk of developing multiple and larger leiomyomata at younger ages than their white counterparts.

Prevention

As the fibroids are estrogen and progesterone dependent, they occur in a large portion of women during their fertile period, and currently, no effective method of prevention that would simultaneously preserve the woman’s fertility is currently known.

Fibroids are related to infertility. There is a general agreement that submucosal leiomyomas negatively affect fertility, when compared to women without fibroids. Submucosal fibroids have a statistically significant negative effect on clinical pregnancy rates as reported by a meta-analysis of 13 studies, the study also showed a lesser extent of intramural fibroids on clinical pregnancy rates. About delivery rates, submucosal and intramural fibroids showed a negative impact. On the contrary, subserosal myomas did not show any effect on clinical pregnancy rates and delivery rates. Thus, submucous and intramural LMs are more involved for sterility and infertility cases due to alteration of uterine cavity and contractility, while subserosal fibroids do not seem to generate any obvious fertility issue.

However, it is still not entirely clear how fibroids may cause infertility. The possible mechanism of impairing fertility also depends on the localization of the fibroid. As mentioned above, the type of fibroids most commonly associated with reduced fertility are submucosal fibroids. It is possible that these fibroids divert the blood flow from the overlying region of endometrium (uterine lining), which impairs its growth and proper function, and may prevent the embryo from successfully implanting.

A much more rare cause of reduced fertility are subserosal fibroids. Depending on their localization, large subserosal fibroids can obstruct the opening of the uterine tubes into the uterine cavity, preventing the embryo from entering the cavity and implanting. Very large or multiple fibroids that alter the overall shape of uterine cavity may be also associated with adverse pregnancy outcomes, such as miscarriage or abnormal fetal presentation, as the deformed uterus is not able to properly accomodate the developing fetus.

Most of the fibroids do not cause any symptoms and are well tolerated by the patients. During pregnancy, the fibroids may grow rapidly due to elevated estrogen and progesterone levels, but they usually tend to shrink back after childbirth. Depending on their size and localization, fibroids may interfere with fertility, usually by preventing the egg from entering uterine cavity or preventing the embryo from inplanting. In treatment of symptomatic fibroids, the specific method is decided on individual basis, mainly considering the severity of patient’s symptoms. Conservative approaches are preferred in fertile women due to possible risks of uterine surgery. For women after menopause, the definitive treatment of fibroids that continue to cause symptoms is hysterectomy.

Find more about related issues

Diagnoses
Adenomyosis

Medical condition characterized by the presence of ectopic endometrial tissue within the myometrium.

Uterine fibroids

The most common benign smooth muscle tumors of the uterus encountered in women of reproductive age.

Gallery
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Sources

“Prevalence, symptoms and management of uterine fibroids: an international internet-based survey of 21,746 women” ―by Zimmermann et al. licensed under CC BY 2.0
“UTERINE FIBROIDS” ―sourced from Fertilitypedia.org licensed under CC BY-SA 4.0
“Uterine fibroid” ―sourced from Wikipedia licensed under CC BY- SA 3.0
“A Comprehensive Review of the Pharmacologic Management of Uterine Leiomyoma” ―by Lewis et al. licensed under CC BY 4.0
“Uterine Fibroids: From Molecular Oncology to Reproduction” ―by Tinelli et al. licensed under CC BY 4.0
“Submucous Fibroids, Fertility, and Possible Correlation to Pseudocapsule Thickness in Reproductive Surgery” ―by Tinelli et al. licensed under CC BY 4.0
“Uterine fibroids” ―by Hic et nunc licensed under CC BY-SA 3.0
“Leiomyoma” ―Ed Uthman licensed under CC BY 2.0
“Fibroid localizations” ―by Hic et nunc licensed under CC BY-SA 3.0
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