Background: The effects of endometrial scratching (ES) on embryo implantation have been studied for many years. Several studies have shown better outcomes when performed on patients undergoing intrauterine insemination and in vitro fertilization (IVF) cycles, but many other reports have not been able to find these differences. As far as cycles with donor eggs are concerned, reported evidence is scarce. Our aim in this trial is to determine if ES is useful for those patients undergoing IVF cycles with donor eggs, in order to assure a greater homogeneity in embryo quality and endometrial preparation.Methods: This single centre randomized controlled trial will include patients undergoing an egg donation cycle, meeting the inclusion criteria and who accept to participate in the study. Once informed consent is signed, patients will be randomly allocated to the study arm (group A) and then receive ES in the luteal phase of the cycle prior to embryo transfer, or the control arm (group B) without any intervention. All cycle data will be collected and analyzed to obtain the clinical pregnancy and the live birth rates in the two groups.Discussion: Several studies have tried to determine the effectiveness of an ES in IVF cycles, but it is still unclear due to the heterogeneity of these reports. The aim of this study is to determine if there are differences in clinical pregnancy rate and live birth rate in egg donor cycles, when comparing an ES performed in the preceding luteal phase versus no intervention, given that embryo quality and endometrial preparation protocols will be comparable.Trial registration: Ethical approval of version 2.0 of this trial was obtained on the 13th January 2017. It was retrospectively registered on the 5th April 2017 as the ENDOSCRATCH Trial (NCT03108157) in ClinicalTrials.gov.

Endometrial scratching (ES) has been proposed as a useful technique to improve outcomes in in vitro fertilization (IVF) cycles, particularly in patients with previous implantation failures. Our objective was to determine if patients undergoing egg-donor IVF cycles had better live birth rates after ES, according to their previous implantation failures. Secondary outcomes were pregnancy rate, clinical pregnancy rate, ongoing pregnancy rate, miscarriage rate, and multiple pregnancy rate. We analysed the results of 352 patients included in the Endoscratch Trial (NCT03108157). A total of 209 were patients with one or no previous implantation failures (105 with an ES done in the previous cycle, group A1, and 104 without ES, group B1), and 143 were patients with at least two previous failed implantations (71 patients with ES, group A2, and 72 without ES, group B2). We found an improvement in pregnancy rates (62.9% in group A1 vs. 55.8% in group B1 vs. 70.4% in group A2 vs. 76.4% in group B2, p = 0.028) in patients with at least two previous implantation failures, but this difference was not statistically different when we compared clinical pregnancy rates (59.1% vs. 51.0% vs. 64.8% vs. 68.1% in groups A1, B1, A2 and B2, respectively, p = 0.104) and live birth rates (52.4% vs. 43.3% vs. 57.8% vs. 55.6% in groups A1, B1, A2 and B2, respectively, p = 0.218). According to these results, we conclude that there is no evidence to recommend ES in egg-donor IVF cycles, regardless of the number of previous failed cycles.