A patient who is one week postpartum starts to notice bright red bleeding. Which of the following is the most likely cause of this finding?

Choice A rationale Endometritis is an infection of the endometrium, the uterine lining, typically presenting with fever, uterine tenderness, foul-smelling lochia, and sometimes delayed uterine involution. While it can cause abnormal bleeding, the bleeding is often purulent or foul-smelling, and the finding of bright red (active hemorrhage) bleeding one week postpartum is less classically associated with this late-onset infection. Choice B rationale Normal postpartum discharge, or lochia, changes color over time. For the first few days (Lochia Rubra), it is bright red. By one week postpartum, the typical discharge is Lochia Serosa, which is thinner, watery, and pinkish-brown. The return to bright red bleeding one week postpartum is a deviation from the normal progression and warrants further investigation for potential pathology. Choice C rationale Retained placental fragments prevent the complete and sustained contraction of the myometrial muscle fibers, which are essential for clamping down on the uterine blood vessels (living ligatures). This lack of sustained vasoconstriction and compression can lead to late postpartum hemorrhage, often manifesting as intermittent or sudden onset of bright red vaginal bleeding one or more weeks after delivery. Choice D rationale Cervical tears typically occur during the trauma of delivery and are a common cause of immediate postpartum hemorrhage (within 24 hours of birth) where the uterus is firm but bleeding persists. While they can continue to bleed, a cervical tear causing new-onset or sudden bright red bleeding one week postpartum is less common than a condition related to the uterine cavity's involution, like a retained placenta.