Endometrial injury (EI) was first described as a beneficial procedure for women with RIF during IVF treatments by Barash et al. in 2003. In this procedure, also known as endometrial scratching, the endometrium is locally intentionally damaged, usually by a Pipelle catheter. The underlying mechanism, through which endometrial injury improves implantation, is still not completely clear. There are three main supposed theories. First is through inducing decidualization of endometrium, which might improve the transferred embryos implantation. Second is that the process of healing after endometrial injury involves an inflammatory reaction mediated with cytokines, interleukins, growth factors, macrophages and dendritic cells, which are beneficial to embryo implantation. The third is that endometrial injury in previous cycle leads to better synchronicity between endometrium and transferred embryos through retarding endometrial maturation.
Many studies have been published on the efficacy of EI and its true benefit on reproductive outcome, including several reviews and meta‐analyses, and basic science studies. Improved clinical pregnancy rates (CPR) and live birth rates (LBR) have been apparent mainly in younger patients, while other studies have suggested improved reproductive outcomes in women with two or more previous failed cycles, with the greatest beneficial effect seen when double luteal EI was performed. Whilst globally accepted as a technique that can possibly improve implantation rates in selected patients, it still remains debatable the optimal timing of the procedure and whether it takes more than one EI to induce a proper immunological response.
