What is your subsequent management plan?

Case Study: A 32-year-old woman presents to the clinic for an acute visit 6 days following a vaginal delivery at 39 weeks gestation. The pregnancy and labor had been unremarkable and the placenta was delivered by controlled cord traction. Following delivery, the woman had been discharged home after 48 hours. She reported that the lochia had been heavy for the first 2 days but that it had settled to less than a period. However, today she had suddenly felt crampy abdominal pain and felt a gush of fluid, followed by very heavy bleeding. The blood-soaked through clothes and she had passed large clots, which she describes as the size of her fist. She feels dizzy when she stands up and is nauseated. Examination She is pale with cool and clammy extremities. She is also drowsy. Her blood pressure is 105/50 and heart rate is 112/min. On abdominal palpation there is minimal tenderness but the uterus is palpable approximately 6 cm above the symphysis pubis. Speculum examination reveals large clots of blood in the vagina. When these are removed, the cervix is seen to be open. Questions: What is the diagnosis? What is your immediate management plan? What is your subsequent management plan? Should an ultrasound be ordered?