P-295 Consequences of embryos transfer following fresh biopsy (single vitrification) and frozen-thaw embryo biopsy (double vitrification) after preimplantation genetic testing for aneuploidy: A retrospective cohort analysis

Study question Does exposure of embryos to double vitrification and double warming affect the chances of ongoing pregnancy for patients undergoing embryo biopsy and euploid embryos transfer? Summary answer A significantly higher statistical clinical outcomes were established in fresh embryo biopsy as compared to freeze-thaw embryo biopsy cycles. What is known already In couples and clinicians, often uncertainty is observed while testing cryopreserved embryos for embryo selection via preimplantation genetic testing for aneuploidy (PGT-A). The utilization of PGT-A over the years has been augmented and leads to the lowering down of the genetic disorders in neonates. The effect of transferring euploid thaw, biopsy, refreeze (TBR) embryos is inconclusive and ESHRE PGT Consortium and SIG Embryology good practice recommendations of 2020 depicted that multiple cryopreservation and its impact on pregnancy outcomes requires further investigations. This investigation aims to uncover the effects of transferring a freeze-thaw biopsy embryos in comparison to fresh biopsy embryos. Study design, size, duration It is a single centric retrospective observational study conducted during the timeline of May 2021 to September 2024 with data of 181 frozen euploid embryo transfers (FETs). The research had two arms, embryos underwent fresh PGT-A, control group (n = 114) and embryos underwent freeze-thaw PGT-A, comparative group (n = 67). The research included a maximum of two grade 1 embryo transfers and the bias was eliminated by matching the patient’s characteristics and indications and embryo morphology. Participants/materials, setting, methods In fresh PGT-A group, the embryos were cultured till day5 or 6 using standard protocol and PGT-A was performed by aspirating 5-10 cells from trophectoderm and vitrified until transfer. In the freeze-thaw PGT-A group (previous failure) the good embryos vitrified on day5 or 6 were thawed for PGT-A and re-vitrified until transfer. The clinical outcomes in the groups were estimated. Statistical analysis was performed using chi-square and Fisher Exact test and p < 0.05 was considered significant. Main results and the role of chance Our investigation decodes that in the freeze-thaw embryo biopsy (n = 67) a reduction in clinical pregnancy rate (CPR) of 17.5% was observed compared to fresh embryo biopsy (n = 114) (59.7%, 77.2%; p = 0.018). CPR is defined as the presence of a vital fetal heart observed at 6-8 weeks scan. For biochemical pregnancy rate (BPR) a decrease of 15.9% was seen in the freeze-thaw embryo biopsy group compared with the control group (65.7%, 81.6%; p = 0.020). The pregnancy of the patients was tracked till 12 weeks (ongoing pregnancy rate) and a decline of 15.2% was observed in freeze-thaw embryo biopsy group compared with the control group (56.7%, 71.9%; p = 0.048). Simultaneously, the trimester losses were also calculated, and it was observed that biochemical loss rate was higher by 3.7% in patients underwent freeze-thaw embryo biopsy as compared to controls. However, the first trimester loss was higher in control group by 1.8% compared to freeze-thaw embryo biopsy group. The difference in biochemical loss and first trimester loss failed to attain significance. Limitations, reasons for caution This is a retrospective observational study. To elucidate the underlying insights of impact on pregnancy outcomes after euploid TBR transfer, a prospective comparative analysis is required. Wider implications of the findings The investigation depicts that if the embryo diagnose via PGT-A has to be performed, then patients must be counselled, and PGT-A must be conducted on fresh embryos. The multiple vitrification maybe necessary in amplification failures but could have an adverse impact on reproductive outcomes even for good quality blastocysts. Trial registration number No