A 5 cm corpus luteum cyst will gradually disappear in about 2-3 months. Luteal cysts tend to occur in the reproductive age and are functional cysts. The size and appearance of the corpus luteum varies greatly in adult women. After ovulation, the follicular wall collapses, the follicular membrane blood vessels rupture, blood bodies are formed, the remaining granulosa cells become larger, and the cytoplasm is enriched with yellow granular lipid-like material to form the corpus luteum. The diameter of the normal corpus luteum is usually less than 2cm, and when the corpus luteum reaches 3cm in diameter, it is called the cystic corpus luteum. If the cystic corpus luteum persists or increases in size, or if the corpus luteum hematoma contains more blood and is absorbed, luteal cysts can result. Anticoagulant therapy and congenital anaplastic fibrinogenemia are prone to cause luteal cysts. Luteal cysts usually have no clinical symptoms. If the cyst persists, lower abdominal pain, amenorrhea or delayed menstruation may occur. Sexual intercourse may cause the cyst to rupture or it may rupture on its own. If it is accompanied by delayed menstruation, it is easy to misdiagnose it as a ruptured ectopic pregnancy. The final diagnosis is often made on the basis of caesarean section and pathologic examination. Luteal cysts occasionally cause ovarian torsion. If a 5-cm corpus luteum cyst does not disappear after 2-3 months, the gynecology department of a regular hospital should be consulted to determine whether there is a pathologic cause.