Controlled ovarian hyperstimulation adversely affects implantation following in vitro fertilization-embryo transfer

Purpose: Our purpose was to determine if controlled ovarian hyperstimulation adversely affects implantation. Methods: A retrospective comparison of pregnancy rates (PRs) and implantation rates was made between oocyte recipients versus their donors, who shared half of the retrieved oocytes, and regular patients undergoing in vitro fertilization-embryo transfer (IVF-ET) who were not sharing eggs. Results: Higher implantation rates (39.0 vs 22.5%; P < 0.05) were found in recipients compared to donors in the stimulated cycle. However; no differences were seen in PRs or implantation rates in frozen ET cycles. The data for standard IVF patients were almost-identical to those for donors. Conclusions: Superior implantation rates and PRs in oocyte recipients versus donors were nor related to better oocyte quality for recipients because of egg sharing or to a better uterine environment because of similar results with frozen ET in all three groups. An adverse effect of the hyperstimulation regimen best explains the difference.