The effect of endometrial scratch on pregnancy outcomes of frozen-thawed embryo transfer: a propensity score-matched study

Aims To study the effect of endometrial scratch (ES) performed on Days 2 to 5 of the menstrual cycle on pregnancy outcomes of frozen-thawed embryo transfer (FET). Materials and methods We conducted a retrospective study including 5769 women undergoing FET from January 2018 to August 2019. The endometrial scratching group (group ES) consisted of 827 patients and the control group (group non-ES) comprised 4942 patients. A propensity score matching (PSM) method using the nearest neighbor matching at a proportion of 1:1 was performed. Subsequently, we compared the pregnancy outcomes of each group after PSM. Results After PSM, there were significant differences in implantation (36.1% vs. 47.0%, p = .005), clinical pregnancy (45.4% vs. 58.3%, p = .007), and live birth (33.5% vs. 47.2%, p = .003) rates in matched patients with two previous implantation failures. In the matched patients with at least three previous implantation failures, we also detected increase rates of implantation (31.0% versus 40.1%, p = .028), clinical pregnancy (39.8% versus 57.0%, p = .019), live birth (32.3% versus 47.3%, p = .036). In contrast, no significant difference in pregnancy outcomes was found in women with no previous implantation failure or only one failure. Conclusions Endometrial scratch on day 2 to day 5 of the menstrual cycle in women with at least two previous implantation failures who underwent FET increased their implantation, clinical pregnancy, and live birth rates, and did not increase miscarriage or ectopic pregnancy rates compared to the non-ES group.