Postpartum hemorrhage refers to blood loss of more than 500 m1 within 24 hours after delivery of the fetus, and is a serious complication during labor and delivery, ranking first among the causes of maternal death in China. Its incidence accounts for 2% to 3% of all deliveries, and the actual incidence is higher due to the difficulty of collecting and measuring blood loss during delivery, and the estimated blood loss is low. The main causes of postpartum hemorrhage are weak uterine contractions, placental factors, soft birth canal lacerations and coagulation disorders. These causes can coexist, be causal or interact with each other. 1.Lack of uterine contraction is the most common cause of postpartum hemorrhage. Factors affecting the contraction and contraction function of the uterine muscle can cause uterine contraction weakness bleeding. Common factors are: (1) systemic factors ① maternal mental overstress, fear of childbirth; ② physical weakness or combined with chronic systemic diseases, etc. (2) Obstetrical factors ① prolonged labor and delivery makes excessive physical exertion; ② anterior placenta, placenta abruptio, hypertensive disease during pregnancy, uterine cavity infection, etc. can cause uterine muscle edema or oozing blood, affecting the contraction function. (3) uterine factors ① excessive stretching of uterine muscle fibers (multiple pregnancy, excessive amniotic fluid, huge fetus); ② injury to the uterine muscle wall (history of cesarean section, post myomectomy, too many deliveries, emergency delivery, etc.); ③ uterine pathology (uterine fibroids, uterine malformations, uterine muscle fiber degeneration, etc.). (4) Drug factors: excessive use of sedatives, anesthetics or uterine contraction inhibitors after delivery. If the placenta is not expelled after 30 minutes, the blood sinus on the abruptive surface of the placenta cannot be closed and causes postpartum bleeding. The common reasons are: ① bladder filling: the abruptive placenta stays in the uterine cavity; ② placenta entrapment: improper application of uterine contraction drugs, circular contraction of the uterine muscle near the endocervical opening, causing the abruptive placenta to entrap in the uterine cavity; ③ incomplete abruptio placenta: premature pulling of the umbilical cord or pressure on the uterus during the third stage of labor, affecting the normal abruptio placenta, and bleeding due to the opening of the blood sinus of the abruptio incomplete position. (2) Placental adhesion or placental implantation The placental villi only penetrate into the superficial layer of the uterine wall for placental adhesion; the placental villi penetrate into the myometrium of the uterine wall for placental implantation, both of which can be classified as partial or complete. Partial placental adhesion or implantation is manifested by partial abruption of the placenta and partial non-abruption, resulting in poor contraction of the uterus and fatal bleeding from the opening of the blood sinuses on the abrupted surface. Complete placental adhesions and implantations have no bleeding because the placenta is not detached. Common causes include multiple abortions, uterine infections that damage the endometrium and primary metaplastic dysplasia. (3) Partial placenta remnants The placenta lobules or parietal placenta remain in the uterine cavity, affecting the uterine contraction and causing bleeding, sometimes part of the fetal membrane remains in the uterine cavity and also causes bleeding. Soft birth canal laceration Soft birth canal laceration is not detected in time, resulting in postpartum bleeding. Common reasons include vaginal surgery to assist delivery (such as forceps assisted delivery, breech traction, etc.), delivery of huge children, emergency delivery, poor elasticity of soft birth canal tissues and excessive force of delivery. 4.Coagulation dysfunction Any primary or secondary abnormalities of coagulation function can cause postpartum bleeding. Primary thrombocytopenia, aplastic anemia and other obstetric comorbidities can cause massive bleeding from postpartum incision and uterine blood sinus due to coagulation dysfunction. Obstetric complications such as placental abruption, stillbirth, amniotic fluid embolism, and severe preeclampsia can cause massive uterine bleeding due to disseminated intravascular coagulation (DIC). Clinical manifestations】 Vaginal bleeding and hemorrhagic shock are the main clinical manifestations of postpartum hemorrhage after delivery of the fetus. 1.Vaginal bleeding ①Vaginal bleeding with bright red color immediately after delivery should be considered as soft birth canal laceration; ②Vaginal bleeding with dark red color several minutes after delivery should be considered as placental factor; ③Vaginal bleeding after delivery of placenta should be considered as lack of uterine contraction or residual placenta or fetal membranes; ④Vaginal bleeding continuously after delivery of fetus and blood does not clot should be considered as coagulation dysfunction; ⑤Blood loss is obvious with vaginal pain and vaginal bleeding without hemorrhagic shock If the fetus is delivered with vaginal pain but not much vaginal bleeding, consider occult soft birth canal injury, such as vaginal hematoma. 2, shock symptoms appear irritable, skin pale and wet cold, pulse fine, pulse compression hours, the mother may be in early shock.