MSERM – Prediction of Ipplantation Rate in Single Euploid Frozen-Thawed Blastocyst Transfer Cycles by Culture Time And /OR Re-Expansion Rate After Trophectoderm Biopsy

Track: ART – LAB
Poster : ART Lab: Basic
Vasileios Stolakis
Senior Embryologist-
Andrology Laboratory Supervisor
Kofinas Fertility Group
New York, New York

Objective: To examine whether the culture time and/or re-expansion rate after trophectoderm (TE) biopsy can predict implantation rate in single euploid frozen-thawed blastocyst transfer (seFET) cycles. DESIGN: Retrospective cohort study in a private assisted reproductive technology (ART) program. MATERIALS AND

Methods: In this retrospective cohort study 397 blastocysts (Day-5 and -6) from 344 patients (35.8 ± 4.2 years of age) were characterized as euploid after preimplantation genetic screening by array comparative genomic hybridization or next generation sequencing. The TE biopsies and the (seFET) cycles were performed at the Kofinas Fertility Group ART clinic from January 2016 to January 2020. All aneuploidy screenings were authorized by patients after consultation. The euploid blastocysts of all participants were divided in two groups: (i) those that were cultured for 1-4 h after TE biopsy (Cultured Group; CG, n=184) and (ii) those that were cryopreserved immediately after TE biopsy (Non-Cultured Group; NCG, n=213). In addition, the CG was further divided in two subgroups based on the re-expansion rate after TE biopsy in relation to the initial blastocoel expansion rate; these subgroups were either: (i) partially re-expanded (pRE) blastocysts (blastocoel formation, but not full re-expansion) or (ii) fully re-expanded, hatching or completely hatched blastocysts (fRE). Implantation rate was assessed in the examined groups and subgroups.

Results: No significant difference was detected in the overall implantation rate between the two examined groups, CG and NCG (70% vs 69%, respectively) and between the two subgroups of the CG group, pRE and fRE (70% vs 71%, respectively). In contrast, Day-5 euploid blastocysts that belong to the pRE subgroup demonstrated a significantly higher implantation rate compared to Day-6 euploid blastocysts belonging to the same subgroup (78% vs 52%, respectively, p<0.01). Most importantly, euploid blastocysts cultured for ≤2h after biopsy belonging to the fRE subgroup were characterized by a significantly higher implantation rate when compared with euploid blastocysts cultured for more than 2h after biopsy belonging to the pRE subgroup (83% vs 54% respectively, p<0.05).

Conclusions: Implantation rate in seFET cycles can be improved by selecting blastocysts that are able to achieve full re-expansion when cultured for ≤2h after TE biopsy, instead of blastocysts that are cultured for >2h after TE biopsy and they have only partially re-expanded. Further studies are required in order to shed more light on the optimal culture time and/or re-expansion rate after TE biopsy.

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