The causes of postpartum hemorrhage can be summarized into four main reasons: First is related to the placenta; second is lacerations in the soft birth canal; third is coagulation dysfunction; fourth is uterine atony, among which uterine atony is the most common cause. So, how can one determine if postpartum hemorrhage is caused by uterine atony? Clinically, after the placenta is delivered, examination of the soft birth canal is conducted. Upon examining the uterus, if it is found that the outline of the uterus is unclear and pressing on it results in a lot of blood and blood clots flowing out from the uterine cavity, then the uterus becomes firm when pressed and softens when not pressed. This situation indicates uterine atony. Other injuries, such as lacerations in the soft birth canal, are generally detected during an examination. There are also factors related to the placenta and coagulation dysfunction, which are the four main causes of postpartum hemorrhage.