In order to maintain normal maternal pregnancy, blocking antibodies are mainly produced by embryonic human class II antigens and trophoblast cross antigens, and combine with maternal lymphoid antigens or placental trophoblast antigens, so as to prevent them from being recognized and killed by the maternal immune system, avoid the occurrence of harmful immune response, and finally achieve the purpose of maintaining normal pregnancy.[27–30] Abnormal increase of PD-1/PD-L1 is not conducive to pregnancy, resulting in abortion.[21]. This evidence concerns the gene CD274 and abortion.