The published studies (summarized in Table 3), differ in terms of (a) population characteristics (infertile vs. exclusively RIF patients), (b) the transferred embryos (cleavage embryos vs. blastocysts, fresh vs. frozen embryos), c) the PBMC activation protocol (no-activation, activation by HCG, activation by corticotropin-releasing hormone-CRH). Here, CRH is linked to Infertility.