Objective: To evaluate the effect of local injury to the endometrium on the day of oocyte retrieval on implantation and pregnancy rates in assisted reproductive cycles. Materials and Methods: In a prospective controlled trial, a total of 156 patients, < 38 years old, in their first IVF cycle were randomized. In 77 patients two small endometrial samples from anterior and posterior walls of uterus were obtained with a Novak curet on the day of oocyte retrieval and in 79 patients no intervention was performed Results: The experimental and control patients were matched regarding women´s age, body mass index, basal FSH, duration and etiology of infertility, treatment protocol, number of retrieved oocyte, endometrial thickness, percentage of intracytoplasmic sperm injection performance, fertilization rate, the percentage of patients with good- and top-quality embryos and the number of embryos transferred. The implantation rate (7.9% vs. 22.9%), clinical (12.3% vs. 32.9%; odds ratio = 0.25; 95% confidence interval = 0.12-0.66; p < 0.05) and ongoing pregnancy (9.6% vs. 29.1%; odds ratio = 0.25; 95% confidence interval = 0.10-0.64; p < 0.05) rates were significantly lower in experimental group, compared with 79 controls. Conclusion: According to the results of this study, local injury to the endometrium on the day of oocyte retrieval disrupts the receptive endometrium and has a negative impact on implantation and IVF outcomes.