An ovarian cyst is a fluid-filled sac that forms on or inside an ovary. Women have two ovaries, and each ovary is about the size and shape of an almond. Eggs develop and mature in the ovaries, and they are released in monthly cycles during the childbearing years. Ovarian cysts are common, and most of the time, they are harmless and go away without treatment within a few months. Most ovarian cysts form as a result of the menstrual cycle, and these are called functional cysts. Other types of cysts are much less common.

Functional cysts are the most common type of ovarian cyst and aren’t disease-related. They occur as a result of ovulation (the release of an egg from the ovary). These cysts can be a sign that your ovaries are functioning as they should. Functional cysts generally shrink over time, usually within 60 days, without specific treatment. Sometimes, functional cysts are called simple cysts.

Ovarian cysts usually only cause symptoms if they split (rupture), are very large, or twist and then block the blood supply to the ovaries. In these cases, women may experience pelvic pain, pain during sex, difficulty emptying their bowels, a frequent need to urinate, heavy periods, irregular periods, lighter periods than normal, bloating, and a swollen tummy.

A cyst on the ovary can be found during a pelvic exam or on an imaging test, such as a pelvic ultrasound. Depending on the size of the cyst and whether its filled with fluid or solid, a healthcare provider will determine the best course of action. Most women will not need treatment for ovarian cysts, but in some cases, surgery may be necessary to remove the cyst.