Closed antibody is a kind of specific IgG antibody against spouse lymphocyte in the serum under normal condition after pregnancy, which can play a role in protecting the embryo through the production of immune reaction. If a pregnant woman has an immune abnormality or genital inflammation, the production of closed antibody will be affected, and the laboratory test will be negative for closed antibody, which means that it cannot protect the embryo, and miscarriage may occur. Clinical examination of closed antibody is often used for women who have had repeated spontaneous abortions, and can be stimulated by spousal leukocyte immunotherapy, but because the safety and effectiveness of this therapy is highly controversial, some medical institutions have stopped this therapy.