They are sometimes called leiomyomas or myomas. Fibroids are extremely common and the number of women affected increases with age until menopause. Symptoms are usually related to the size and number of fibroids and include heavy bleeding, pain, and pressure. It is not known exactly what causes fibroids, however, genetics and hormones are thought to play a role in their development. This explains why fibroids are more common in certain ethnic groups and families, and why pregnancy and menopause affect the size of fibroids.
Pregnancy can cause a significant increase in the size of fibroids.
This is thought to be related to an increase in estrogen levels during pregnancy. Fibroids usually shrink after menopause because the levels of estrogen in the body decrease. However, fibroids can grow after menopause if the person is taking estrogen pills to combat the effects of menopause. This is sometimes called hormone replacement therapy. Heavy menstrual bleeding is the most common symptom.