A, Representative pictures of Ki67 staining in the human endometria obtained from women at the time of embryo implantation. Samples were divided into two groups according to the outcome of clinical pregnancy following endometrial biopsy. Scale bar = 100μm; le, luminal epithelium; s, stroma. B, Ratio of Ki67-positive cells in the human uterine luminal epithelium during the implantation period was lower in the group with pregnancy than the group without pregnancy (mean ± SEM, Student's t test; n=10 different individuals for each group). Three different high-powered fields per sample were analyzed and each of the Ki67-posivie ratios was demonstrated. 