The uterine fibroids are benign (non-cancerous) tumors located on the lining of the uterus, singly or in groups.

Also called myomes, méiomyomes ou uterine fibromyomas, fibroids usually appear in women after the age of 30. They can vary in size from the size of a pea to that of a grapefruit, or even more.

In the majority of cases, fibroids do not cause any symptoms. However, sometimes they can be very bothersome and cause heavy menstrual bleeding, all kinds of pain and frequent urges to urinate. In addition, fibroids sometimes cause fertility problems.

Prevalence

Le uterine fibroids is the most common non-cancerous tumor in women of childbearing age. It is estimated that 20% to 40% of Caucasian women and up to 50% of African American women over the age of 35 have uterine fibroids. After 50 years, this proportion increases to 70% in Caucasian women and to 80% in those of African origin.¹. However, more than half of these fibroids do not cause no symptoms, it is therefore difficult to estimate their exact prevalence.

Types

There are 3 types of uterine fibroids, depending on their location (see the diagram at the top of the sheet).

• The interstitial or intramural fibroids. They form in the muscular layer of the wall of the uterus. They represent almost 70% of all fibroids.
• The subserous fibroids. They grow outside the uterus and are sometimes attached to it by a pedicle.
• The submucosal or endocavitary fibroids. These fibroids take up space in the uterine cavity because they form under the lining of the uterus. These fibroids are the rarest, but they often cause heavy bleeding.

Causes

Little is known about the cause of fibroids. Their existence is probably the result of a set of factors genetic, hormonal and environmental.

It seems that the fibroid originates from a single cell in the uterine wall that undergoes a genetic mutation and begins to multiply out of control. Subsequently, the estrogen (female hormones) act on this fibroid and stimulate its growth.

Heredity also seems to play a big role. If a mother has had a fibroid, her daughter is more likely to have them too.

Evolution

The natural course of most uterine fibroids is to increase in size. A high level of estrogen in the body accelerates the growth of fibroids. Being pregnant, taking birth control pills, or taking hormone therapy increases the amount of estrogen in the body. Paradoxically, clinical studies have shown that fibroids do not increase during pregnancy². However, 2% to 4% of pregnant women have a fibroid that develops during pregnancy.

As for taking oral contraceptives (a combination of estrogens and progestins), the studies are contradictory, but most show that the contraceptives slow down the growth of the fibroid, especially when they are formed early in adolescence.^{3 4}.

At the start of perimenopause, estrogen levels are usually higher, which often triggers fibroid growth a few years before menopause. After menopause, fibroids gradually regress due to the decline in estrogen production, and if they are not too large, eventually they will go away. Hormone replacement therapy after menopause rarely results in a slight growth of fibroids⁵. Indeed, the doses of estrogen contained in these replacement hormones are very low.

Complications

Most uterine fibroids go unnoticed and have no health consequences. But in some cases complications can be associated with it and result in:

• of the hemorrhages. When a fibroid causes heavy loss of health, it can even lead to anemia;
• a decreased fertility. Most women with fibroids are fertile and have normal pregnancies. However, a large fibroid can decrease the fertility blocking the fallopian tubes or preventing implantation of the embryo;
• problems during pregnancy. Pregnant women who have fibroids are more likely to miscarry and give birth prematurely. This risk, however, depends on the size and location of the fibroid in the uterus.⁴;
• la organ compression neighbors. If the fibroid is large, it can compress the bladder, rectum, or ureters, which are the ducts that connect the kidneys to the bladder. This can be a source of pain and more or less serious complications (urine retention, constipation, etc.).