#66 : Degree of Re-Expansion of Biopsied Blastocysts at Vitrification Affects the Developmental Competence of Blastocyst After Trophectoderm Biopsy

Abstract

Background and Aims: In recent years, preimplantation genetic testing (PGT) has frequently involved a trophectoderm (TE) biopsy at the blastocyst stage, followed by vitrification. However, the factors influencing the viability of biopsied blastocysts after warming are unknown. Thus, these factors should be determined before developing the vitrification protocol following TE biopsy. The present study aimed to analyze the association between the time intervals between biopsy and vitrification, morphological characteristics after the biopsy, and blastocyst outgrowth. Methods: In this study, we used discarded vitrified blastocysts donated for research by consenting couples. To observe the morphological changes, TE biopsies were performed and cultured in a time-lapse incubator. Based on the degree of re-expansion at vitrification, the blastocysts were classified into four groups: 0%, 1-49%, 50–99%, and ≥100%. The blastocysts were vitrified after 0–3 h of TE biopsy. The warmed blastocysts were cultured on fibronectin-treated dishes for 96 h to examine the competence of the outgrowth. Results: The outgrowth area was significantly less extensive in the blastocysts that were vitrified 2 h following the biopsy. The proportion of 50–99% of re-expansion was significantly higher in the blastocysts after 2 h of biopsy. Multivariate linear regression analysis showed that the blastocyst outgrowth area was substantially smaller when the degree of re-expansion was 50–99%. Conclusions: Vitrification of blastocysts in the late stages of re-expansion following TE biopsy impairs the developmental competence of the blastocyst. Therefore, while vitrifying blastocysts after TE biopsy, we should consider the time intervals after the biopsy as well as the progression of re-expansion.