This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'Cause of secondary PPH is \nSelect and explain. \nA. Atonic uterus, B. Retained placental bits, C. Ruptured uterus, D. Cervical laceration', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Causes of secondary PPH: Retained bits of cotyledon or membranes Infection and separation of slough over a deep cervicovaginal laceration Endometritis Hemorrhage from cesarean section wound Withdrawal bleeding following estrogen therapy for suppression of lactation Ref: Dutta Obs 9e pg 392.', 'role': 'assistant'}]