I. Definition In the serum of normal pregnant women, there is a specific IgG antibody against the spouse’s lymphocytes that inhibits the lymphocyte response (MLR), shuts down the cytotoxic effect of maternal lymphocytes on the cultured trophectoderm, prevents the recognition of suppressors of fetal antigens by helper T cells, and prevents the attack of the mother’s immune system on the embryo. Blocking homologous antigen-stimulated lymphocytes produce macrophage movement inhibitory factor (MIF), so it is called blocking antibody (blockingantibody; BA). In vitro studies have shown that the mother can produce sensitized T cells during pregnancy, which can destroy embryonic cells. However, the killing function of sensitized T cells can be inhibited by sexual antibodies, however, about 80%-90% of women with habitual abortion do not detect such specific blocking antibodies, and there are unsuppressed cytotoxic cells in the body. These cells can act directly on the embryo or indirectly damage the fetus or placenta by releasing inflammatory mediators, resulting in miscarriage. III. Clinical significance Modern reproductive immunology considers pregnancy as a successful semi-identical transfer process that protects the mother from foreign microorganisms and maintains the continuation of pregnancy without immune rejection of intrauterine embryo grafts when maternal immune function is normal. Recurrent spontaneous abortion (RSA) occurs twice or more consecutively and accounts for 0.5% to 3% of total pregnancies. Its pathogenesis is complex, involving genetics, reproductive endocrinology and other etiologies, and the causes are unknown in about 41.18% to 60.00% of cases, 80% of which are related to immune factors. Antiphospholipid antibody (APLA) is a type of IgG antibody produced by human leukocyte antigen (HLA), trophoblast and lymphocyte cross-reacting antigen (TLX) that stimulates the maternal immune system. It is believed that APLA in maternal blood can exhibit the following effects: (1) APLA neutralizes allogeneic antigens without rejection of the fetus; (2) antibodies act directly on immunocompetent cells such as CTL cells and NK cells; and (3) binds directly to antigens of target cells, thereby reducing their sensitivity to immune responses involving receptor cells. Previous studies have suggested that the occurrence of recurrent spontaneous abortion is associated with maternal APLA deficiency, and that the greater the number of miscarriages, the greater the likelihood of APLA deficiency in the patient’s body. insufficient APLA production results in strong maternal rejection of the fetus, which can occur in early pregnancy with recurrent spontaneous abortion, and in late pregnancy with gestational hypertension, intrauterine growth restriction, or even intrauterine fetal death. Therefore, it is necessary to perform APLA test for patients with recurrent spontaneous abortion. IV. Specimen collection The laboratory department of our hospital introduced the American BDFACSCalibur automatic double-laser four-color flow cytometer, which is the most advanced method for detecting closed antibodies. 2ml of blood was drawn from the stem tube of the female side and 4ml from the heparin anticoagulation of the husband on the second floor of the outpatient laboratory.