Termination of pregnancy at less than 28 weeks of gestation and fetal weight less than 1000g is called miscarriage. Miscarriages occurring before 12 weeks of gestation are called early miscarriages, while those occurring between 12 and less than 28 weeks of gestation are called late miscarriages. The incidence of spontaneous abortion accounts for about 15% of all pregnancies, and most of them are early abortions. There are also two special types of miscarriages: freak miscarriage and habitual miscarriage. Who are prone to miscarriage? 1, endocrine dysfunction, such as luteal insufficiency, insufficient progesterone in the body, which affects the development of pregnant eggs, or low thyroid function, which can cause impairment of cellular oxidation process and affect the development of embryo and cause miscarriage. 2. Patients with reproductive organ diseases may suffer from uterine malformations such as bicornuate uterus, longitudinal uterus, uterine dysplasia, pelvic tumors (uterine fibroids, especially submucosal fibroids) that affect the development of the uterus and lead to miscarriage. Loose endocervix or deep cervical laceration leads to premature rupture of fetal membranes and midterm miscarriage. 3, patients with systemic diseases Acute infectious diseases cause direct damage to the placenta by maternal poisoning, such as infection, typhoid and other bacterial toxins or viruses can enter the fetal blood circulation through the placenta and cause fetal death. High fever can cause uterine contractions and miscarriage. Chronic diseases, such as severe anemia or heart failure, can cause miscarriage due to severe hypoxia. Chronic nephritis or hypertension, placental infarction can lead to miscarriage. 4, physical trauma During pregnancy, surgery (such as appendicitis or ovarian cystectomy to interfere with the abdomen to stimulate the uterus), bruises, overexertion or sexual intercourse can stimulate uterine contractions and cause miscarriage. 5, mother-child blood type incompatibility mother-child blood type incompatibility is due to the blood type incompatibility between the pregnant woman and the fetus resulting in homozygous blood group immune disease. The fetus inherits blood group antigen from the father that the mother lacks, and this antigen enters the mother’s body through the placenta, which can stimulate the mother to produce the corresponding immune antibodies, or due to previous pregnancy, blood transfusion, Rh factor and incompatible ABO blood group factor in the mother to produce antibodies, and this antibody enters the fetus through the placenta, the combination of antigen and antibody can cause the fetus red blood cell agglutination and destruction, hemolysis, which may be the This may be the cause of mid-term miscarriage. 6, exposure to toxic and harmful substances Early pregnancy has been exposed to toxic substances, drugs, radiation, excessive smoking or intrauterine infection and other effects that cause serious deformities or even death of the embryo or fetus, stimulating the uterus contraction to expel it out of the body resulting in miscarriage. In addition, the factors that cause miscarriage on the father’s side should not be ignored, as male asymptomatic bacteriospermia can lead to spontaneous abortion, and male exposure to toxic and harmful substances can affect the quality of sperm, resulting in abortion due to malformation of the embryo or fetus.