“…During the implantation process, the blastocyst regulates the expression and secretion of integrins β3, α4 and α1 (Simón et al, 1997), the interleukin-1 (IL-1) system (De los Santos et al, 1996), chemokines IL-8, MCP-1 and RANTES (CaballeroCampo et al, 2002), leptin (Cervero et al, 2004;González et al, 2000) and hCG (Licht et al, 2001;Paiva et al, 2011) by the endometrial epithelium during the window of implantation (WOI), the period when the endometrium is receptive to a blastocyst. The EF, a viscous fluid secreted by the endometrial glands into the uterine cavity, nurtures the embryo and constitutes the microenvironment in which the first bidirectional dialogue between the maternal endometrium and the embryo occurs during the WOI (Cha et al, 2012(Cha et al, , 2013Thouas et al, 2014;Tranguch et al, 2005).…”