A 29-year-old woman presents for heavy vaginal bleeding. She is hemodynamically stable. She had an uncomplicated vaginal delivery of a full-term baby 1 week ago. She denies fever or pain. There is active bleeding from the os. No cervical motion tenderness or signs of trauma or foul-smelling discharge. What is the most likely diagnosis?
A. Uterine Atony
B. Retained products of conception
C. Cervical Trauma