The exact cause and pathogenesis of placental abruption is unknown, and may be related to the following factors: 1. Pregnant women with vascular lesions, hypertensive disorders during pregnancy, especially severe preeclampsia, chronic hypertension, chronic kidney disease and systemic vascular lesions are prone to placental abruption. 2. sudden decrease in intrauterine pressure, premature rupture of fetal membranes, twin pregnancies, too rapid delivery of the first child during labor, excessive amniotic fluid, manual rupture of membranes The placenta may be aborted due to the sudden drop of pressure in the uterine cavity and contraction of the uterus. 3, mechanical factors, trauma, especially direct impact and extrusion on the left side of the abdomen, short umbilical cord and umbilical cord around the neck, fetal descent during labor, pulling the umbilical cord, puncture of the blood vessels at the placental attachment of the anterior wall during amniocentesis, formation of hematoma after the placenta, causing placental abruption. 4, other high-risk factors, with such as Advanced maternal age, menstruating women, smoking, abnormal metabolism of pregnant women, tendency of pregnant women to thrombosis, pregnant women with uterine fibroids, etc.