Closed blastocyst vitrification of biopsied embryos: evaluation of 100 consecutive warming cycles

BACKGROUND The aim of this study was to analyse the outcome of closed blastocyst vitrification of embryos biopsied at the cleavage stage.
METHODS Vitrification of supernumerary blastocysts was performed using the closed CBS-VIT High Security straws. Warming cycles (n= 100) for patients with preimplantation genetic diagnosis (PGD) and/or aneuploidy screening in the fresh cycle were analysed. The outcome parameters were morphological survival and transfer rates after warming, clinical pregnancy rate and implantation rate (with fetal heart beat). Clinical outcome was compared with two control groups of (i) vitrified/warming transfer cycles without embryo biopsy and (ii) fresh Day 5 transfer of biopsied embryos.
RESULTS In total, 131 blastocysts were warmed with a morphological survival of 83.2% (109/131) and a transfer rate of 79.4% (104/131). Day 5 blastocysts survived significantly better (90.4%) than Day 6 blastocysts (70.8%, P<0.01). No difference in survival rate was observed between early cavitating (89.2%) and full/expanded blastocysts (93.3%). In nine cycles, no blastocyst was available for transfer. The clinical pregnancy rate was 19.2% (15/78) after single-embryo transfer (SET) and 38.5% (5/13) after double-embryo transfer (DET). In SET, the implantation rate for blastocysts frozen on Day 5 was 13.7% (7/51), which was not different from the implantation rate of Day 6 blastocysts (18.5%, 5/27). The overall implantation rate of vitrified PGD biopsied blastocysts (14.4%) was comparable with that of vitrified blastocysts without biopsy (20.4%), but lower than the implantation rate obtained in the fresh PGD cycles (24.4%).
CONCLUSION Blastocysts on Day 5 and Day 6 of development derived from biopsied embryos can be successfully vitrified using a closed system.