Uterine fibroids are noncancerous uterine growths that typically occur during pregnancy and grow in and on the uterus. The uterus is an upside-down pear-shaped organ located in the pelvis. Your uterus should be approximately the size of a lemon. It’s also known as the womb, and it’s where a baby develops and grows when pregnant. Uterine fibroids, also known as leiomyomas (lie-o-my-O-muhs) or myomas, are not connected with an increased risk of uterine cancer and seldom progress to cancer.