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What is a functional ovarian cyst?
An ovarian cyst is a round, thin-walled, clear fluid-filled sac that develops in the ovary as part of normal egg development. When on the ovary's surface, an ovarian cyst looks something like a skin blister. A normal ovarian cyst can grow as large as 1.5 in.(3.8 cm) as it prepares to release an egg into the abdomen (ovulation).

When an ovarian cyst does not release its egg, it continues to grow, becoming larger than normal (functional ovarian cyst). A functional ovarian cyst may also form after an egg is released. In this case, the ovarian cyst reseals itself and swells with fluid. This is called a luteal cyst. Functional ovarian cysts are the most common type of ovarian growth in women of childbearing age.

Like most types of ovarian cysts, functional cysts usually don't cause symptoms and are first noticed during a general pelvic exam. However, a larger ovarian cyst can twist, rupture, or bleed and be very painful. If your health professional has found that you have a functional ovarian cyst, you have no reason to worry about cancer-functional cysts do not lead to cancer. Most functional ovarian cysts go away on their own within a few months and are harmless.

What causes functional ovarian cysts?
A functional ovarian cyst is caused by one or more slight changes in the way the ovary produces or releases an egg. Although unlikely, it is possible to ovulate while taking hormonal birth control pills and, therefore, to be capable of developing a functional ovarian cyst.

What are the symptoms?
Most functional ovarian cysts are harmless, do not cause symptoms, and go away without treatment. However, they can cause symptoms such as:

Lower abdominal pain or ache, typically in the middle of your menstrual cycle.
Menstrual period delay.
Weight gain.
Unexpected vaginal bleeding.

Some functional ovarian cysts can twist or rupture and bleed. Symptoms include:

Sudden severe pain, often with nausea and vomiting (possible sign of a twisted cyst).
Pain immediately after intercourse (possible sign of a ruptured cyst).

If you have symptoms that suggest a twisted or ruptured ovarian cyst, call your health professional immediately. Some ruptured cysts bleed enough that treatment is necessary to prevent heavy blood loss.

How are functional ovarian cysts diagnosed?
If your health professional discovers an ovarian cyst during a routine pelvic exam, he or she may use a pelvic ultrasound to make sure the cyst is fluid-filled (functional), then recommend a watchful waiting period and recheck you after a couple of menstrual cycles. A functional ovarian cyst is likely to go away on its own during this period of time.

How are they treated?
Most functional ovarian cysts go away without treatment within 1 to 3 menstrual cycles. If you have a functional cyst that persists through 2 to 3 menstrual cycles or that causes symptoms, your health professional will probably recommend birth control pills, which stop the ovulation process. Birth control pills should prevent new functional cysts from developing, but they may not speed up the shrinkage of an existing cyst.