Human in vitro fertilization (IVF) embryos usually have developmental block at 4-8 cell stages,in which only 30％-50％ percent of IVF embryos develop to blastocyst stage.This is the main cause for low efficiency and repeated treatment failure in human fertility therapy.Transcription factor CDX2 is one of the key genes in human early embryonic development,which decides the differentiation from blastomere to trophoblastic lineage.However,the relationship between the developmental block of human IVF embryos and CDX2 is poorly understood.In this study,we showed that CDX2 is crucial for human IVF embryonic development.q-PCR analysis confirmed that the level of CDX2 in developmental block embryos was dramatically decreased.Immunofluorescence analysis further demonstrated that CDX2 protein level in developmental block embryos was significantly decreased compared with that in control embryos.We also addressed whether reexpression of CDX2 could rescue developmental block defects in human IVF developmental block embryos.As expected,these developmental block defects could be partially rescued by overexpression of CDX2 protein.In conclusion,these findings suggest that CDX2 plays an important role in the process of human early embryonic development.