Abstract: Cyclosporin A is a macrolide immunosuppressant widely used to suppress immunological rejection after organ transplantation and to treat autoimmune diseases. Recently， researches on application of CsA in Obstetrics and reproduction have been carried out and revealed that CsA could induce the maternal?鄄fetal immunity tolerance, enhance proliferation, movement, migration, invasion of trophoblasts, and inhibit apoptosis of trophoblasts. CsA regulates early pregnancy from two aspects above, so it is expected to be a clinical medicine for unexplained recurrent spontaneous abortion（ＵＲＳＡ）. Based on understanding of CsA pharmacodynamic mechanism， CsA could also be applied in assisted reproductive technology（ART）.

Key words: Cyclosporine, Trophoblasts, Immunosuppressive agents, Immune tolerance, Abortion, habitual