Clots and pressure marks on the maternal side of the placenta are symptoms of placental abruption. Sometimes the symptoms and signs of placental abruption are not obvious, and it is only when the placenta is examined after delivery and there are clots and pressure marks on the maternal side of the placenta that placental abruption is detected. After 20 weeks of pregnancy or during labor, the placenta in its normal position is partially or completely detached from the uterine wall before delivery of the fetus, which is called placental abruption. The main symptom of mild placental abruption is vaginal bleeding, which is usually heavy and dark red in color, and may be accompanied by mild abdominal pain or abdominal pain is not obvious, and the signs of anemia are not obvious. The main symptom of severe placental abruption is the sudden onset of persistent abdominal pain and/or lumbago, lumbar pain, the degree of which varies according to the size of the stripped surface and the amount of blood accumulation after the placenta, the more blood accumulation, the more severe the pain. 1, the common causes of placental abruption Most of them are hyperemesis gravidarum, due to poor perfusion of uteroplacental blood flow, which can lead to varying degrees of infarction, necrosis, and easy to occur placental abruption. 2, the umbilical cord is too short The umbilical cord connecting the fetus and the placenta, if it is too short or the umbilical cord around the neck and wrapped around the limbs, then in the process of delivery, the fetus is gradually under the relative short, when short than the descent, especially strong contractions, descending too fast, due to the umbilical cord length is not enough to pull the placenta and placental detachment from the uterine wall. 3, the pressure in the uterine cavity decreases suddenly. The first fetus of a twin pregnancy is delivered too quickly; excessive amniotic fluid, in the natural or artificial rupture of membranes when the amniotic fluid flows out in large quantities, so that the pressure in the uterine cavity decreases suddenly, and the uterus contracts suddenly, which can cause the placenta to be misplaced in the uterine wall at the place of attachment and detachment. 4.Mechanical factors: trauma (especially direct impact on the abdomen or fall on the abdomen directly touching the ground, etc.), external inversion surgery to correct the fetal position, the umbilical cord is too short or the umbilical cord around the neck, in the process of labor and delivery of the fetal prelude to the Department of the decline, may contribute to the premature detachment of the placenta. In addition, if the first fetus of twin pregnancy is delivered too fast or the amniotic fluid is too much, the amniotic fluid flows out too fast when the membranes are broken, so that the pressure in the uterus suddenly decreases and the uterus suddenly contracts, which can also lead to placental abruption from the wall of the uterus. 5, the uterine venous pressure suddenly rise in late pregnancy or after delivery, pregnant women take a long time to supine position, can occur supine hypotension syndrome. At this time, due to the huge pregnancy uterus compression of the inferior vena cava, reduce the volume of cardiac blood, blood pressure drops, while the uterine veins are stagnant, venous pressure rises, resulting in ecchymotic venous bed stasis or rupture, resulting in part or all of the placenta from the uterine wall peeling. 6, vascular lesions placental abruption pregnant women complicated by severe hyperemesis gravidarum, chronic hypertension and chronic kidney disease, especially those who have systemic vascular lesions. When the bottom of the meconium spiral artery spasm or sclerosis, caused by distal capillary ischemia and necrosis to rupture bleeding, blood flow to the bottom of the meconium layer to form a hematoma, resulting in placenta from the wall of the uterus peeling.