Corpus luteum cyst

A Corpus luteum cyst is a type of ovarian cyst which may rupture about the time of menstruation, and take up to three months to disappear entirely. This type of functional cyst occurs after an egg has been released from a follicle. The follicle then becomes a secretory gland that is known as the corpus luteum. The ruptured follicle begins producing large quantities of estrogen and progesterone in preparation for conception. If a pregnancy doesn't occur, the corpus luteum usually breaks down and disappears. It may, however, fill with fluid or blood, causing the corpus luteum to expand into a cyst, and stay on the ovary. Usually, this cyst is on only one side, and does not produce any symptoms.^[1][2]

It can however grow to almost 10cm (4 inches) in diameter and has the potential to bleed into itself or twist the ovary, causing pelvic or abdominal pain. If it fills with blood, the cyst may rupture, causing internal bleeding and sudden, sharp pain. The fertility drug clomiphene citrate (Clomid, Serophene), used to induce ovulation, increases the risk of a corpus luteum cyst developing after ovulation. These cysts don't prevent or threaten a resulting pregnancy.^[3][4] Women on birth control pills usually do not form these cysts; in fact, preventing these cysts is one way the combined pill works.^[5] In contrast, the progesterone-only pill can cause increased frequency of these cysts.

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