Abstract: Repeated implantation failure (RIF) refers to failure of achieving a clinical pregnancy after transferring several good-quality embryos in several IVF/ICSI cycles. The causes are complicated, in matrix, including abnormal anatomical structure, bad receptivity of endometrium, disorder immune state; in embryo factors, including abnormal hereditary substance, inappropriate incubation and implantation. How to detect the exact causes of RIF and appropriate pretreatment are the key to improve the prognosis of RIF. The methods include, in matrix, correcting abnormal anatomical structure through surgery, increasing endometrial thickness, suppressing frequent uterine contraction, regulating coagulation function and immune state, improving response of endometrium et. al; as to embryo, screening good-qualify embryos, assisting hatching embryos and improving implanting skills.

Key words: Fertilization in vitro, Embryo transfer, Repeated implantation failure, Embryonic development, Endometrium, Immune tolerance