Endometritis: This is the most common cause of postpartum fever, especially after a vaginal delivery. It is an infection of the uterus that can occur after childbirth, miscarriage, or abortion. The risk factors include prolonged labor, prolonged rupture of membranes, and multiple vaginal examinations during labor.

Urinary Tract Infection (UTI): UTIs are common in the postpartum period due to factors like catheterization during labor and postpartum urinary retention. Symptoms can include fever, dysuria, and flank pain.
Breast Engorgement/Mastitis: Breast engorgement is common in the first few days postpartum, and if not properly managed, can lead to mastitis, an infection of the breast tissue. Symptoms include fever, breast pain, and swelling.
Wound Infection: If the patient had an episiotomy or perineal laceration during delivery, a wound infection could be a cause of fever. Symptoms include increased redness, swelling, and purulent discharge from the wound site.

Septic Pelvic Thrombophlebitis: A rare but serious condition where a blood clot in the pelvic veins becomes infected. It can present with persistent fever despite antibiotic treatment for endometritis.
Pulmonary Embolism: Although less common, pulmonary embolism is a critical diagnosis to consider in any postpartum patient with fever, especially if there are respiratory symptoms or risk factors for thromboembolism.
Sepsis: Any infection in the postpartum period can lead to sepsis, a life-threatening condition. Early recognition and treatment are crucial.

Infected Hematoma: A collection of blood outside of blood vessels that becomes infected. This could occur in the uterus, vagina, or at the site of an episiotomy.
Necrotizing Fasciitis: A rare but severe infection of the tissue beneath the skin and the fascia, a layer of tissue covering muscles, nerves, fat, and blood vessels in the affected area. It requires prompt surgical intervention.