If puerperal fever occurs between 24 hours and 10 days after delivery, it should be considered as puerperal infection first. In addition to puerperal infection, puerperal fever has the following causes: 1. cold. Postpartum fatigue, decreased resistance, easy to catch cold and flu. In addition to fever, it is often accompanied by nasal congestion, runny nose, cough, sore throat and other symptoms. Generally with symptomatic treatment, the body temperature will drop. 2. Pyelonephritis. There are symptoms such as frequent urination, urgent urination, painful urination and back pain, as well as percussion pain in the kidney area of the waist and abnormal urine routine examination. It requires hospitalization for anti-inflammatory treatment and can return to normal. 3. Mastitis. Acute mastitis often occurs 2 to 6 weeks after delivery, with localized redness, swelling, heat and pressure pain in the breast, and fluctuating sensation if it has become septic. After treatment with antibacterial agents, the temperature may drop. 4.Milk swelling. Some new mothers have milk distension 2 to 3 days after delivery because the milk ducts are not fully cleared, which may also cause fever, but generally does not exceed 38℃. After the milk is discharged smoothly, the body temperature will also drop. 5.Puerperal heatstroke. It often occurs in the summer heat season due to high temperature. However, there are also other seasons, mainly due to high indoor temperature, lack of ventilation and too thick clothing.