Abstract: Apoptosis is a cascade of events played an important role during pregnancy，it plays crucial roles in cytotrophoblast differentiation into syncytiotrophoblast. Trophoblast invasion ensures the anchoring of the placenta within the uterine wall and the access of the fetus to the maternal vascular system to assure the supply of oxygen and nutrients. Apoptosis of EVT limits uterine invasion. Peptides from apoptotic EVT cells serve as inducers to establish a local tolerance during the 2nd trimester. The apoptotic cascade monitoried by the mother's immune system. The immune status of pregnant women is not significantly reduced in comparison with that of non-pregnant women. Maternal immune system is able to recognize and react against the foreign antigens of the "fetal transplant". A specific tolerance induction mechanism interconnects EVT limitation and tolerance at the feto-maternal interface. Cytokines are secreted predominantly by T-cells and NK cells，and Leukocytes exert their action through cytokines which resemble paracrine immune response modulators. Apoptotic process regulated by genes，hormones，and oxidative stress，etc.

Key words: Apoptosis, Pregnancy, Histocompatibility, maternal-fetal, Immune tolerance, Immunologic surveillance