But I couldn't afford the ultrasound or another visit to the doctor. I'm scared it might be cancer. Fibroids are balls of muscle tissue that form on or in the uterus, an organ mostly made up of smooth muscle. Genetics plays a part in susceptibility to fibroids, which are so common that more than half of all women in their 40s have most likely had at least one. Certain cells in the uterus seem to develop into lumps due to sensitivity to estrogen.
Fibroids tend to swell up during pregnancy when estrogen levels soar and shrink after menopause.
Most fibroids cause no symptoms and are discovered during routine pelvic exams. If the fibroids aren't causing discomfort, treatment is not usually necessary. Some women with fibroids have very heavy menstrual bleeding and can become anemic. Others experience severe menstrual cramps. Both of these problems seem to be related to the location of fibroids, rather than just their existence.