Induced abortion is a special case of miscarriage, which refers to the death of the embryo or fetus that remains in the uterine cavity and has not been expelled automatically, also known as premature abortion. The incidence of the disease is quite high, 15-20% in women of childbearing age, but its cause is still unclear. The common causes are as follows: 1. immune factors 1. cytokines are involved in the immune regulation between mother and fetus, teratogenic factors such as cyclophosphamide and toxins such as lipopolysaccharide can cause transitional apoptosis of embryonic cells mediated by cytokines such as tumor necrosis factor, and the relative deficiency of Th2 cytokines can lead to the occurrence of abortion. 2. 2. The occurrence of miscarriage may be related to the dysregulation of CD4+/CD8+ T-cell ratio, gonorrhea and the shift of Thl/Th2 functional subpopulation to Thl. The presence of five anti-reproductive immune antibodies in the body: anti-cardiolipin antibody (ACA), anti-sperm antibody (ASAb), anti-endometrial antibody (EMAb), anti-human chorionic gonadotropin antibody, and anti-ovarian antibody (AOA) may be one of the causes of indolent abortion. 4.Blood group incompatibility has ABO and RH blood group incompatibility. In China, the ABO blood group disorder is mainly caused by the mother being type 0 and the fetus being type A or B. When the ABO blood group disorder occurs, the mother produces IgG antibodies to the A or B antigen, and the IgG antibodies can penetrate into the placenta to produce antigenic antibody reactions leading to abortion. There are also reports in the literature that RH blood group incompatibility can lead to miscarriage. Endocrine factors 1. Insufficient secretion of progesterone can cause poor metaphase response, which can affect the implantation and development of pregnant eggs and lead to miscarriage. 2.Human chorionic gonadotropin HCG is a glycoprotein hormone synthesized by the syncytial trophoblast cells of the human placental chorionic membrane. In the early stage of pregnancy, HCG transforms the menstrual corpus luteum into the gestational corpus luteum, which secretes progesterone and prevents the rejection of the embryo from being laid, and also inhibits the rejection of the fetus and placenta by the mother. The decrease in the level of these hormones can lead to the occurrence of induced abortion. 3. PRL has the effect of promoting protein synthesis and causing positive nitrogen balance, so it can promote fetal growth. Animal tests and isolated granule cell culture have confirmed that when PRL decreases to a certain level, the corpus luteum stops developing and inhibits the production of progesterone, while excessive PRL can lead to luteal insufficiency, so patients with hyperprolactinism may have a higher chance of miscarriage than normal women. Genetic factors Chromosomal abnormalities include numerical and structural abnormalities. Chromosomal abnormalities can affect the development of the embryo and lead to miscarriage. Social and environmental factors 1. Studies have shown that computer rays are objectively harmful to the embryo and can cause miscarriage. 2.Exposure to relatively high concentration of sulfur dioxide during the perinatal period may increase the risk of miscarriage in early pregnancy. 3. Longer daily travel time of pregnant women, frequent cooking during pregnancy, history of home renovation during pregnancy, and history of toxic exposure of the husband in the first trimester may have adverse effects on the normal growth and development of the embryo, while the risk of abortion may be relatively small in pregnant women with higher education level. V. Various infections 1. Studies have suggested that mixed infections of Chlamydia trachomatis (CT) and Mycoplasma hyopneumoniae (UU) are the etiology of abortion, and simple CT and UU infections can be one of the causative factors. 2. Studies have shown that HIV infection can cause abortion. TORCH infection is a general term for Toxoplasma gondii (TOX), rubella virus (RV), cytomegalovirus (CMV), herpes HSV) and other intrauterine infections (0). Studies have found that TORCH infection can cause induced abortion. VI. It may be associated with oxidative stress response. VII. May be associated with hypoxia-inducible factor-la (HIF-la) expression. viii. It may be related to reduced diamine oxidase (DOA) activity. In conclusion, we can find out that abortion is a multifactorial disease and the occurrence of abortion may be the result of several factors together.