“…Opening the window of receptivity for conceptus attachment to the uterine endometrium (Day 10 to 14) following down-regulation of the uterine epithelial PGR marks a period of conceptus growth, development and change in morphology stimulated by the release of multiple uterine growth factors and cytokines [ 2 – 4 ]. During the early peri-implantation period, the endometrium increases the release of epidermal growth factor (EGF) [ 34 – 37 ], insulin-like growth factor-1 (IGF-1) [ 38 – 42 ], FGF7 [ 43 , 44 ], vascular endothelial growth factor (VEGF) [ 45 – 47 ], interleukin 6 (IL6) [ 48 – 50 ], transforming growth factor beta (TGFB) [ 51 – 53 ], and leukemia inhibitory factor (LIF) [ 48 – 50 ] for which the developing conceptus trophectoderm expresses EGF-receptor (EGFR) [ 36 ], IGF1R [ 54 ], FGFR2 [ 55 ], VEGFR1 and 2 [ 45 , 47 ], IL6R [ 50 ], TGFBR1 and 2 [ 52 ], and LIFR [ 50 ]. The increased endometrial release of EGF, FGF7, LIF, and IGF-1 are enhanced in the epithelium during the period of conceptus elongation and estrogen release [ 42 , 44 , 50 , 51 , 55 ].…”