text: Female reproductive system
  The ovaries, fallopian tubes, uterus, cervix and vagina (vaginal canal) make up the female reproductive system.
  Ovarian cysts are sacs, usually filled with fluid, in an ovary or on its surface. Females have two ovaries. One ovary is located on each side of the uterus.
  Each ovary is about the size and shape of an almond. Eggs develop and mature in the ovaries. Eggs are released in monthly cycles during the childbearing years.
  Ovarian cysts are common. Most of the time, you have little or no discomfort, and the cysts are harmless. Most cysts go away without treatment within a few months.
  But sometimes ovarian cysts can become twisted or burst open (rupture). This can cause serious symptoms. To protect your health, get regular pelvic exams and know the symptoms that can signal what might be a serious problem.
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  Most ovarian cysts cause no symptoms and go away on their own. But a large ovarian cyst can cause:
  - Pelvic pain that may come and go. You may feel a dull ache or a sharp pain in the area below your bellybutton toward one side.
  - Fullness, pressure or heaviness in your belly (abdomen).
  When to see a doctor
  Get immediate medical help if you have:
  - Sudden, severe abdominal or pelvic pain.
  - Pain with fever or vomiting.
  - Signs of shock. These include cold, clammy skin; rapid breathing; and lightheadedness or weakness.
  A follicular cyst occurs when the follicle of the ovary doesn't rupture or release its egg. Instead, it grows until it becomes a cyst.
  Corpus luteum cyst
  Changes in the follicle of the ovary after an egg has been released can cause the egg's escape opening to seal off. Fluid builds up inside the follicle, and a corpus luteum cyst develops.
  Most ovarian cysts form as a result of your menstrual cycle. These are called functional cysts. Other types of cysts are much less common.
  Your ovaries grow small cysts called follicles each month. Follicles produce the hormones estrogen and progesterone and break open to release an egg when you ovulate.
  A monthly follicle that keeps growing is known as a functional cyst. There are two types of functional cysts:
  - Follicular cyst. About halfway through your menstrual cycle, an egg bursts out of its follicle. The egg then travels down a fallopian tube. A follicular cyst begins when the follicle doesn't rupture. It doesn't release its egg and continues to grow.
  - Corpus luteum cyst. After a follicle releases its egg, it shrinks and begins producing estrogen and progesterone. These hormones are needed for conception. The follicle is now called the corpus luteum. Sometimes, the opening where the egg came from gets blocked. Fluid builds up inside the corpus luteum, causing a cyst.
  Functional cysts are usually harmless. They rarely cause pain and often disappear on their own within 2 to 3 menstrual cycles.
  There are other types of cysts that are not related to menstrual cycles:
  - Dermoid cyst. Also called a teratoma, this cyst forms from reproductive cells that make eggs in the ovary (germ cells). The cyst can contain tissue, such as hair, skin or teeth. This type of cyst is rarely cancer.
  - Cystadenoma. This type of cyst develops from cells on the surface of an ovary. The cyst might be filled with a watery or mucous material. A cystadenoma can grow very large.
  - Endometrioma. Endometriosis is a condition that causes cells similar to those that line the inside of the uterus to grow outside the uterus. Some of the tissue can attach to the ovary and form a cyst. This is called an endometrioma.
  Dermoid cysts and cystadenomas can become large and move the ovary out of position. This increases the chance of painful twisting of the ovary, called ovarian torsion. Ovarian torsion may reduce or stop blood flow to the ovary.
  The risk of having an ovarian cyst is higher with:
  - Hormonal problems. These include taking a fertility drug that causes you to ovulate, for example clomiphene or letrozole (Femara).
  - Pregnancy. Sometimes, the follicle that forms when you ovulate stays on your ovary throughout pregnancy. It can sometimes grow larger.
  - Endometriosis. Some of the tissue can attach to your ovary and form a cyst.
  - Severe pelvic infection. If the infection spreads to the ovaries, it can cause cysts.
  - Previous ovarian cysts. If you've had one ovarian cyst, you're likely to develop more.
  They don't happen often, but complications can occur with ovarian cysts. These include:
  - Ovarian torsion. Cysts that become large can cause the ovary to move. This increases the chance of painful twisting of the ovary (ovarian torsion). If this happens, you might have sudden, severe pelvic pain and nausea and vomiting. Ovarian torsion can also reduce or stop blood flow to the ovary.
  - Cyst rupture. A cyst that bursts open (ruptures) can cause severe pain and bleeding inside the pelvis. The larger the cyst, the greater the risk of rupture. Vigorous activity that affects the pelvis, such as vaginal sex, also increases the risk of rupture.
  There's no way to prevent most ovarian cysts. But, regular pelvic exams help ensure that changes in your ovaries are diagnosed as early as possible. Be alert to changes in your monthly cycle. Make a note of unusual menstrual symptoms, especially ones that go on for more than a few cycles. Talk to your health care provider about changes that concern you.