4.Blastocyst score affects implantation and pregnancy outcome
In this study all patients had transfers of two embryos that were cultured in sequential media to the blastocyst stage (day 5). When a patient received two top-scoring blastocysts (64% of patients), 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 of the two embryos (21% of patients), the implantation and pregnancy rates were 50% and 70%. The twinning rate for this group was 50%. In contrast, when only low-scoring blastocysts were available for transfer (15% of patients), implantation and pregnancy rates were 28% and 44%, and the twinning rate was 29%. No monozygotic twins were observed in this group of patients. These data demonstrate that it might be desirable that ART should proceed towards a single blastocyst transfer.
Gardner DK et al. (2000): towards a single blastocyst transfer. Fertil. Steril. 73: 1155-1158