1.Definition of recurrent miscarriage The occurrence of ≥3 consecutive spontaneous miscarriages before 28 weeks of gestation is called recurrent miscarriage or habitual miscarriage. 2.Clinical classification of recurrent miscarriage According to the etiology and pathogenesis, recurrent miscarriage can be divided into two types: non-immune recurrent miscarriage and immune recurrent miscarriage, which are divided into six types. 2.1 Chromosomal abnormality type: refers to miscarriage caused by chromosomal abnormalities in both or one of the spouses or embryos. 2.2 anatomical abnormalities of the reproductive tract: refers to miscarriage caused by anatomical abnormalities of the uterus, which includes congenital developmental abnormalities and/or anatomical abnormalities caused by acquired uterine diseases. 2.3 Endocrine abnormalities: mainly refers to miscarriage due to endocrine dysfunction. 2.4 Reproductive tract infection type: mainly refers to miscarriage due to Toxoplasma gondii, cytomegalovirus, herpes simplex virus and other infections. 3 Immune recurrent miscarriage 3.l Autoimmune type: mainly refers to miscarriage due to antiphospholipid antibodies, which actually belongs to the category of antiphospholipid antibody syndrome. The diagnostic criteria for antiphospholipid antibody syndrome are at least one of the following clinical symptoms (recurrent miscarriage or thromboembolism) and one positive laboratory indicator for antiphospholipid antibodies. The current antiphospholipid antibody test indicators are: (i) anti-cardiolipin antibody (ACL); (ii) anti-β2GP-l antibody; and (iii) lupus anticoagulant factor (LAC). 3.2 Homozygous immune type: The diagnosis of this type of miscarriage is an exclusion diagnosis, that is, chromosomal, anatomical, endocrine, infectious and autoimmune etiologies are excluded and no other cause of miscarriage is found, which is called homozygous immune type and can also be called recurrent miscarriage of unknown cause. 4. Treatment of immune-type recurrent miscarriage 4.1 Autoimmune type: low-dose, short-course, individualized immunosuppressive and anticoagulant therapy is used, as follows. Immunosuppressive therapy uses low-dose prednisone, the indication is persistent positive or moderate to high level of antiphospholipid antibodies, the drug dose 5mg/d, the time of administration: determine the pregnancy to start the drug, the length of the drug course according to the antiphospholipid antibody level changes: frequent positive or persistent positive drug until the end of pregnancy; during the use of antibody levels turn negative 1-2 months can be considered to stop the drug. In combination with SLE, prednisone dosing and usage are based on the SLE treatment plan. Anticoagulation therapy is low-dose aspirin and/or low-molecular heparin. 4.2 Homozygous immune type Small dose active immunotherapy with lymphocytes. Subcutaneous injections at 3-week intervals. After the first course, the patient is encouraged to become pregnant within 3 months, and if pregnancy is obtained to proceed with 1 more course. If pregnancy is not achieved, a new course of immunization is administered if infertility is ruled out. Homozygous patients should be tested for the presence of platelet activation status and hypercoagulability, and if so, a combination anticoagulation regimen based on active immunization with aspirin and/or low molecular heparin should be administered as above. 5.1 The karyotypic analysis should include not only the couple but also the karyotype of each pregnancy expulsion specimen. ˇ 5.2 Uterine anatomical abnormalities should first be examined by non-invasive methods, mainly ultrasound methods, and in cases where ultrasound examination is not definitive, official cavity microscopy and HSG can be performed. Cervical function examination: ultrasound examination was performed at 12 and 20 weeks of gestation, respectively, and 200 ml of water bladder was placed in the vagina to observe morphological changes in the cervical canal. If the length of the cervix is less than 2.6 cm and the inner diameter of the cervical canal is equal to or greater than 0.5 cm, cervical insufficiency can be diagnosed and cervical cerclage will be performed. 5.3 Endocrine abnormalities should be screened to exclude luteal insufficiency, PCOS, hyperprolactinemia, thyroid dysfunction and diabetes mellitus. 5.4 Infectious diseases are mainly screened for cytomegalovirus, toxoplasmosis and herpes simplex virus. 5.5 Recurrent miscarriages of unknown origin and immune recurrent miscarriages, further analysis of autoimmune and alloimmune types is crucial: antiphospholipid antibody determination using dual indicators (anti-cardiolipin antibody and anti-β2GP-1 antibody) multiple times (at least five times with an interval of June) to improve the rate of antiphospholipid antibody detection in order to reduce missed diagnosis of auto-RSA and improve the accuracy of diagnosis of alloimmune RSA .