Physicians refer to the benign tumors that can develop in a woman's uterus as fibroids, or uterine leiomyomas. Benign uterine growths are the most common cause of abnormal vaginal bleeding. Indeed, fibroids account for one-third of abnormal vaginal bleeding cases. Such bleeding can occur between periods of menstruation, or during menstruation in the form of excessively heavy bleeding.

It is estimated that approximately 30 percent of women over the age of 35 have uterine fibroids. However, only certain types of uterine fibroids can lead to bleeding. As part of making a diagnosis, doctors will first rule out the presence of more dangerous malignant uterine tumors. This is especially the case for women who are nearing or experiencing menopause as they are at the highest risk for developing uterine cancer. At this point, doctors do not believe that benign fibroids can become malignant. However, in menopausal and postmenopausal women, rapidly growing fibroids can indicate that cancer is present in the uterus.

Fibroids may vary in size from small, barely visible nodules, to massive tumors that fill the pelvis. Whatever the size, a characteristic whorled pattern of smooth muscle bundles usually makes fibroids readily identifiable upon inspection by a physician.

Because fibroids can distort the shape of the uterus, they can cause many reproductive problems. These include recurrent miscarriage, infertility, premature and/or complicated labor, and birth defects. Women who wish to become pregnant and are known to have uterine fibroids may wish to have a pelvic exam before attempting pregnancy.

Fibroids may also disrupt the functions of the excretory system by compressing the bladder. This can cause an excessive need to urinate, as well as uncontrollable urination.

There seems to be an increased risk of fibroids in women of color, and in larger women. Conversely, the risk seems to decrease in women who have given birth and in women who smoke.