The purpose of this study is to find out the possible relationship among TWEAK/Fn14, JAK/STAT3 and IDO as well as their roles in the dysfunction of immune micro-environment of endometrium in people diagnosed as repeated implantation failure after in vitro Fertilization-embryo transfer(IVF-ET). We will use the technology of Western-blot and Immunohistochemistry to find out the relationship of the expression of TWEAK/Fn14, JAK/STAT3 and IDO in endometrium . Also, we will use technology of Western-blot and Immunohistochemistry to determine whether there are differences of the the expression of TWEAK/Fn14, JAK/STAT3 and IDO in endometrium between RIF group and control group.