Normally, upon ovulation the mature egg is released and the sac around is also goes away. Sometimes, when the egg is released the sac, instead of going away, closes again. Other times, the egg is not released and stays inside the sac. Fluid fills up in the sac and ultimately converts into a cyst on the surface of ovary. This cyst is called Functional Ovarian Cyst. These are common occurrences and often resolve on their own in 1-3 months. Usually, there are no symptoms. However, when the cysts don’t resolve on their own they grow in size and tend to twist the ovary. It is a medical emergency. The symptoms of Functional Ovarian Cysts are - Severe pain - Fever - Vomiting - Dizziness - Weakness