Outcome of blastocyst transfer according to availability of excess blastocysts suitable for cryopreservation.

The purpose of this study was to assess the outcome of blastocyst transfer in relation to the presence or absence of excess blastocysts available for cryopreservation. The study was designed as a retrospective case series in a tertiary care private hospital. The study group consisted of 450 blastocyst stage embryo transfer cycles. In 139 cycles there were excess freezeable blastocysts (group 1), in 78 cycles there were excess but unfreezeable blastocysts (group 2), and in 233 cycles there were no excess blastocysts (group 3). A mean of three blastocysts was replaced in all groups. Treatment cycle characteristics, implantation and pregnancy rates following fresh and cryopreserved blastocyst transfer were assessed in each group. More embryos reached the blastocyst stage in group 1 and more blastocysts were of good quality. In group 1, clinical pregnancy and implantation rates (71 and 41%) were significantly higher compared with groups 2 (56 and 27%) and 3 (43 and 19%). Embryos that were selected for transfer among a cohort of good quality blastocysts yielded the highest implantation and pregnancy rates. Given a clinical pregnancy rate of 71%, an implantation rate per embryo of 41%, and a multiple pregnancy rate of 58%, serious consideration should be given to a single blastocyst transfer in these patients.