As shown in this study, STAT3 is activated in both epithelium and stroma on days 1 and 4 of pregnancy, LIF is expressed in the luminal and glandular epithelium on day 1 and expressed in the glandular epithelium on day 4, and Lif null female mice exhibit infertility due to implantation failure5. This evidence concerns the gene LIF and Infertility.