What Causes Sudden Blood Loss And The Mass Protruding From The Introitus Post-delivery?

Your patient for today is Argielyn Castr0, a 32 year-old G4P4, vaginally delivered a 4,330gms term male infant 45 minutes ago. She had an uncomplicated prenatal course, and her only medications during pregnancy were prenatal vitamins. Her membranes ruptured at home 48 hours prior to delivery, and she was admitted to Phinma Upang General Hospital [labour and delivery] about 2 hours ago in active labour. Her labour progressed quickly, and she delivered an hour later. After delivering the placenta, there was a gush of blood and the uterus was no longer palpable in the abdomen. There is also a mass protruding in the introitus. The patient said, Masakit ang balakang ko!”. Her most recent vital signs were as follows: Pulse = 88 BPM BP = 124/70 mmHg Resp Rate = 20bpm Temp = 37.1 C O2 Saturation = 97% on room air.      The doctor immediately stops the oxytocin drip and gave Nitroglycerin then performed Johnson’s Maneuver. After the maneuver, the doctor resumed the oxytocin drip and started Cefuroxime 750mg IV as her antibiotics