Five years of single embryo transfer with anonymous and non-anonymous oocyte donation

Single embryo transfer (SET) has been the main embryo transfer strategy in the oocyte donation programme at the authors' clinic since 2000. The primary aim of this study was to evaluate the effect of SET on the clinical outcome in an unselected group of oocyte recipients. A retrospective analysis of the outcome in 142 recipient cycles (116 from anonymous donors; 26 from known donors) was performed. The oocytes from each anonymous donor were shared between two recipients if at least 10 oocytes were obtained. The proportion of SET of all fresh transfers was 77.3%. The clinical pregnancy rate (CPR) was 43.2% and the delivery rate 31.1% per embryo transfer. The outcome was similar in recipients undergoing anonymous and non-anonymous donation. The delivery rates were similar after SET (30.4%) or double embryo transfer (DET) (33.3%), whereas the twin rate was 0% after SET and 40% after DET. The implantation rate was significantly better (P < 0.01) with good-quality embryos (54.7%) compared with non-optimal embryos (27.1%). Of 152 frozen–thawed embryo transfer cycles, 78.9% were SET. The CPR was 28.3% and the twin rate was 7.1%. In fresh oocyte donation cycles, elective SET can be recommended if the embryo quality is considered good, and always if there is a contraindication for twin pregnancy.