They are extremely common, especially in women over 35 and in African-American women. The number, size, and location of the growths determine their effect. Other signs of fibroids include pain during intercourse and pressure or pain in the abdomen and lower back. Generally, if a woman has fibroids, she'll have quite a few, though it's possible to have just one.
Fibroids can range from the size of a pea to the size of a grapefruit.
Their cause is unknown, but it's clear that estrogen stimulates their growth. That's why fibroids do not start growing until after puberty, when a woman's body starts to produce the hormone. Unless a woman starts hormone replacement therapy , the growths should shrink when she reaches menopause and her body stops producing estrogen. While they almost never become cancerous, fibroids can cause infertility. So if you do have them, it's important for your doctor to keep a close eye on them.