Small haemorrhages in cysts are common as both the theca interna and corpus luteum are well vascularised. As with cyst rupture haemorrhage most commonly occurs on days 20-26 of the menstrual cycle. Large cysts can cause bleeding severe enough to cause haemorrhagic shock but this is rare.
Blood from an ovarian cyst rupture can irritate the peritoneum, thereby causing abdominal pain. The blood may collect in the ovarian cortex, stretch the capsule and cause severe pain. The amount of bleeding is greater in patients with clotting disorders or those on anticoagulants.