The impact of double vitrification and warming procedures on pregnancy and neonatal outcomes following single euploid blastocyst transfer.

PURPOSE: To evaluate the impact of multiple vitrification-warming on clinical outcomes of embryos that have undergone preimplantation genetic testing (PGT).

METHODS

This retrospective, single-center study involved 512 single frozen euploid blastocyst transfer cycles conducted between January 2018 and January 2024. Using propensity score matching, 105 patients who underwent double vitrification-warming with single biopsy (DVSB) were matched in a 1:4 ratio with 407 patients in the control group, who underwent single biopsy with single vitrification-warming (SVSB). Post-warming suitability for biopsy and clinical outcomes of subsequent frozen-thawed embryo transfer (FET) cycles were evaluated. Obstetrical and neonatal outcomes were also assessed.

RESULTS

A total of 453 blastocysts were warmed, of which 417 (92.1%) exhibited sufficient quality to undergo trophectoderm biopsy. In FET cycles, a significant reduction in the live birth rate was observed with the additional vitrification-warming step (DVSB: 49.5% vs. SVSB: 61.2%). The pregnancy loss rate in the DVSB group was significantly higher compared to the SVSB group (20.6% vs. 12.2%). Neonatal outcomes, including sex ratio, preterm birth rate, and low birth weight rate, did not differ significantly between the two groups.

CONCLUSION

This study suggests that the inclusion of an additional vitrification-warming step in PGT may adversely affect pregnancy outcomes. Furthermore, only a portion of thawed embryos are able to re-expand and progress to the biopsy stage. PGT patients should be informed that undergoing a second vitrification-warming cycle may reduce the likelihood of a successful pregnancy.