| Table 1. Systematized search using the PICOS method. | ||||
| Description | Abbreviation | Question Components | ||
|---|---|---|---|---|
| Population | P | Women who used ARTs had RAR, RIF, and IVF failure. | ||
| Intervention | I | Performance of blood collection or endometrial biopsy for dosage of immune cells and/or inflammatory cytokines before and/or after embryo transfer. | ||
| Comparison | C | Fertile women who achieved clinical pregnancy. | ||
| Outcome | O | Obtained key IS cells and/or secreted cytokines found in peripheral blood or from endometrial cells. | ||
| Study | S | Observational and case-control studies. | ||
ART: Assisted Reproductive Techniques; IVF: In vitro fertilization; RAR: Recurrent Pregnancy Loss; RIF: Recurrent Implantation Failure; IS: Immune System.