Implantation is a process whereby the embryo attaches itself to the endometrium. In humans, the endometrium has a specific period of uterine receptivity, which occurs 5-7 days after ovulation and remains receptive for ~4 days (cycle days 20-24), when embryo implantation starts. Implantation failure refers to the failure of the embryo to reach a stage when intrauterine gestational sac is recognized by ultrasonography. It occurs when the embryo is abnormal or when endometrial function is impaired.~Uterine natural killer (uNK) cells have been implicated to play a role in female reproductive performance. They comprise 70-80% of the total leukocyte population in the endometrium during implantation and early pregnancy. Several studies showed an increased uNK cell density in the endometrium of women with reproductive failure. To better understand the contribution of various immune factors to endometrial function and future pregnancy, it is proposed to examine the major immune cells in the same specimen to measure the relative magnitude of the cell density changes and the degree of clustering between two immune cell types.~The aim of this study is to investigate the endometrial leucocytes profile around the time of embryo implantation.
Uterine natural killer (uNK) cells have been implicated to play a role in female reproductive performance. Serval studies showed an increased uNK cell density in the endometrium of women with reproductive failure. In this study, we wish to investigate the density and clustering of four different immune cells.