Fibroids are classified by their location, which affects the symptoms they cause and how they can be treated. Fibroids inside the uterine cavity (intracavitary myomas) usually cause bleeding between periods and often severe cramping. Submucous myomas are partly in the cavity and partly in the uterine wall. They too can cause heavy periods, as well as bleeding between periods.

A fibroid is a benign (non-cancerous) tumor of the uterus. Fibroids consist of smooth muscles bundles and connective tissue that grow slowly within the uterine wall. As a fibroid enlarges, it may grow within the muscle so that the uterine cavity is distorted, or it may protrude from the uterine wall into the uterine cavity but remain attached by a stalk. Fibroids may be as small as a pea or as large as a grapefruit, and there may be one or more of them.


Occurrence and cause

Fibroids are among the most common tumors, occurring in about one-fifth of all women over the age of 30. They appear most often in women aged 35 to 45 and seldom before the age of 20.


The cause of fibroids is unknown, but it is thought to be related to an abnormal response to estrogen hormones. Oral contraceptives containing estrogen can also cause fibroids to enlarge, as can pregnancy. Decreased estrogen production after the menopause usually causes them to shrink.



In many cases there are no symptoms, especially if a fibroid is small. If a fibroid grows and erodes the lining of the uterine cavity, it may cause heavy or prolonged menstrual periods (see menstruation); severe bleeding can lead to iron-deficiency anemia. Large fibroids may exert pressure on the bladder, causing discomfort or frequent passage of urine, or on the bowel, causing backache or constipation. Occasionally, a fibroid attached to the uterine wall becomes twisted and causes a sudden pain in the lower abdomen. Fibroids that distort the uterine cavity may be responsible for recurrent miscarriage or infertility.



Symptomless fibroids are often discovered during a routine pelvic examination. When fibroids are thought to be the cause of menstrual disturbances or responsible for other symptoms, ultrasound scanning can confirm the diagnosis.



Small, symptomless fibroids usually require no treatment, but regular examinations may be necessary to determine whether they are growing. Surgery is required for fibroids that cause serious symptoms or complications. A hysterectomy (removal of the uterus) is sometimes considered if there are large numbers of fibroids. Myomectomy (shelling out of the fibroid from its capsule) saves the uterus and is another alternative.