The uterus, or womb, is part of the female reproductive system. Often described as pear-shaped, it is located in the lower abdomen. The uterus lies in close proximity to the ovaries, where unfertilized eggs are stored. During ovulation the eggs travel down the fallopian tubes to the uterus. Fertilized eggs implant and grow in the uterus.

 

Uterine fibroid tumors are the most common type of neoplasm in the female reproductive system (neoplasm is simply another word for tumor). This particular type of neoplasm develops from the smooth muscle tissues of the womb. They are extremely common in women: 20 to 25 percent of women develop uterine fibroid tumors. Most fibroids never cause symptoms and do not require removal. Other names for fibroids are leiomyomas, leiomyomata, fibromyomas, and myomas.

Uterine fibroid tumors are benign growths, and are only very rarely malignant. Less than one percent develop into uterine cancer. These very rare occurrences generally occur in women during menopause. The vast majority of leiomyomas are not life threatening, although some can cause health complications.

A uterine fibroid develops from a single cell in the uterus muscle. The neoplasm may be less than a quarter of an inch long; many measure up to six inches; and a rare few grow as large as ten inches in diameter.

The different types of leiomyomas are classified according to their location:

The exact cause of uterine fibroids is unknown, but hormones are believed to play an important role. The tumors tend to develop faster during the reproductive years, when estrogen and other female hormones are at their highest levels. After menopause, leiomyomas often diminish in size.

Most leiomyomas do not interfere with pregnancy, but size and location can cause complications. The extra blood flow to the womb during pregnancy can stimulate tumor growth. Occasionally, caesarean sections may be required to counteract complications. Possible complications include miscarriage, premature contractions, and premature labor.