Abstract: Tight junction is a fundamental junctional complex of the adjacent epithelial cells consist of several protein families such as transmembrane proteins occludin，claudin and peripheral proteins ZOs. Tight junction performs specialized functions including maintenance of paracellular barrier functions and cell polarity principally. The structure and function of tight junction can bechanged by some physio-/pathological factors. Tight junction has already been detected in human uterine endometrium，placenta and luteal cells. Abnormality of tight junction may correlate with endometrial receptivity，placental implantation and luteal function and also has been involved in the pregnancy complications.

Key words: Endometrium, Placenta, Pre-eclampsia, Tight junctions