Blastocyst score affects implantation and pregnancy outcome: towards a single blastocyst transfer

Objective: To determine the relationship between blastocyst score and pregn ancy outcome. Design: Retrospective review of blastocyst transfer in an IVF clinic. Setting: Private assisted reproductive technology unit. Patient(s): 107 pat ients undergoing blastocyst culture and transfer of two embryos. Intervention(s): Culture of all pronucleate embryos in sequential media to the blastocyst stage (day 5), followed by transfer of two blastocysts. Main Outcome Measure(s): Implantation rates, pregnancy rates, and twinning were analyzed. Result(s): When a patient received two top-scoring blastocysts (64% of pati ents), implantation and pregnancy rates were 70% and 87%, respectively. The twinning rate in this group was 61%. When only one top-quality blastocyst was available for transfer (21% of patients), the implantation and pregnanc y rates were 50% and 70%. The twinning rate for this group was 50%. In cont rast, when only low-scoring blastocysts were available for transfer (15% of patients), implantation and pregnancy rates were 28% and 44%, and the twin ning rate was 29%. No monozygotic twins were observed in this group of pati ents. Conclusion(s): The ability to transfer one high-scoring blastocyst should l ead to pregnancy rates greater than 60%, without the complication of twins. (C) 2000 by American Society for Reproductive Medicine.