Fibroids Patient Information Fact Sheet

What are fibroids?
Fibroids are growths that develop inside the womb (uterus). They are usually noncancerous, and frequently present as more than a singular growth. As many as one  in five women may have fibroids during their childbearing years, while half of all women have fibroids by the age of 50. The medical term for a fibroid is a uterine myoma or fibromyoma (referred to as myomata or fibromyomata if there are multiple fibroids present). Fibroids can cause problems and require treatment, but they are not usually life-threatening. They often develop within the muscle wall of the womb but can also grow in other areas. The symptoms may be different depending on the site of the fibroid(s).

Intramural fibroids form within the muscle wall of the womb itself. If they proceed to grow, they cause the womb to increase in size.

Subserous fibroids grow away from the outer muscle wall of the womb. They can grow on a stalk, which may become twisted.

Submucous fibroids grow inside the womb under the lining (the endometrium) and can cause heavy bleeding.

Occasionally, fibroids can develop in the cervix (cervical fibroids). These can enlarge into the vagina.

A woman may have multiple fibroids of different sizes simultaneously forming in any of these areas.

What are the symptoms of fibroids?
Very often, women have no symptoms and may not even know that they have fibroids. Symptoms are not necessarily related to the size or number of the fibroids, but usually, the bigger or more numerous they are, the more likely they are to cause problems. The most common symptom caused by fibroids is heavy, prolonged periods (menorrhagia). This heavy bleeding may cause some women to become anemic. Fibroids can cause the womb to become bulky and enlarged, causing pressure in the pelvic region. This can result in symptoms such as backache, lower abdominal pain, and the need to urinate more frequently (as a result of pressure on the bladder). Fibroids may cause fertility problems in some women, particularly if the fibroids grow out into the womb and prevent an embryo from implanting.

What causes fibroids?
It is not known what causes fibroids. High levels of estrogen may influence their growth, this is not the root cause. Fibroids can occur in women with children but are more common in women with lower fertility or those without children. Being very overweight may increase the risk of developing fibroids, as body fat produces estrogen independently of the ovaries; however, slim women can also develop fibroids. They are more common in African Americans than Caucasians, and less common in women who smoke.