Objective To investigate the effect of macrophages on embryo implantation by observing the distribution of macrophages in mouse uterine tissues during the peri- implantation period. Methods Uterine tissues were collected from pregnant(n=30) and pseudopregnant mice(n=30) during the peri- implantation period. The distributions of macrophages,i NOS and leukemia inhibitory factor(LIF) were determined by immunohistochemistry and the correlations of macrophages with i NOS and LIF were analyzed. Results Macrophage...