After 20 weeks of gestation or during delivery, the placenta in its normal position is partially or completely detached from the uterine wall before the delivery of the fetus, which is called placental abruption. Placental abruption is a serious complication in late pregnancy, with rapid onset and progression, which can endanger the life of mother and child if not treated in time. The incidence of placental abruption is 4,6‰ to 21‰ in China and 5,1‰ to 23,3‰ in foreign countries. The incidence is related to whether the placenta is carefully examined after delivery. Some mild cases of placental abruption may have no obvious symptoms before delivery, and only during postpartum examination of the placenta, clot pressure is found at the site of abruptio, which is easily ignored in such patients. The abdominal examination shows that the uterus is hard like a plate on palpation and there is pressure pain, especially at the placenta attachment area. The following diseases also cause the uterus to be hard like a plate: 1. Placenta praevia The normal placenta is attached to the posterior, anterior or lateral wall of the uterus. If the placenta is attached to the lower part of the uterus, or even if the lower edge of the placenta reaches or covers the inner cervical opening, and its position is lower than the fetal previa, it is called placenta previa. Placenta previa is one of the main causes of late pregnancy bleeding and is a serious complication of pregnancy, which can endanger the life of mother and child if not treated properly. Its incidence is reported to be 0.24% to 1.57% in China and 1.0% in foreign countries. The incidence of anterior placenta can be as high as 5% in 85% to 90% of patients who are in labor, especially in multiple mothers. 2, the uterus contraction is too strong Labor force includes uterine contraction, abdominal wall muscle and diaphragm contraction and anal raphe contraction, of which the uterus contraction is the main force. During labor, the rhythm, symmetry and polarity of uterine contractions are abnormal or the strength and frequency are changed, which is called abnormal uterine contraction. Clinically, obstructive obstructed labor is often caused by abnormalities in the birth canal or fetal factors, which increases the resistance of the fetus to pass through the birth canal and leads to secondary abnormalities in labor force. Uterine contraction abnormalities are clinically divided into two categories: weak uterine contractions and excessive uterine contractions, each of which is divided into coordinated uterine contractions and uncoordinated uterine contractions. Hypercontraction refers to normal rhythm, symmetry, and polarity of uterine contractions, but only hypercontraction of the uterus.