Why does giving birth cause heavy bleeding

Clinical postpartum hemorrhage is the most common cause of uterine contraction weakness, in addition to three reasons, such as placental factors, soft birth canal laceration, coagulation dysfunction, these four factors are the main cause of postpartum hemorrhage, coexistence and mutual influence. Uterine contraction weakness generally has the following factors: The first is systemic factors, such as maternal over-tension, fear of childbirth, etc. The second is obstetric factors, such as prolonged labor, excessive physical disappearance, placenta previa, placental abruption, pregnancy hypertension, etc., can make uterine edema or ooze blood, affecting uterine contraction. The third is uterine factors, if the uterine muscle fibers are excessively stretched, such as multiple pregnancy, polyhydramnios, giant fetuses, etc. There are also uterine wall injuries, such as caesarean section history, uterine myomectomy, uterine lesions, such as their own uterine malformation or uterine fibroids. The fourth is the drug factor, if labor too much use of anesthetics, sedatives or uterine contraction inhibitors, can also cause uterine atony.