#175 : Cohort Study of Post-Thawed Blastocyst Morphology is Associated with the Clinical Pregnancy of the Single Embryo Transfer Cycle

Background and Aims: Frozen Embryo Transfer is the final step in undergoing IVF treatment. One of the important parts in the success of the FET cycle is the quality of the transferred embryos. The ability of blastocyst post-thawed recovery indicated embryo potential. However, there is limited understanding of the factors that influence recovery of post-thawed blastocyst embryos. This study aims to examine whether blastocyst morphology post-thawed correlates with clinical pregnancy rate.

Method: In a retrospective cohort study, analysis data of Morula IVF Surabaya was conducted from January 2022 – February 2023, thawed blastocyst with a post-thaw cell survival rate of 50%–100% were observed for morphological characteristics prior to transfer. Then, recovery of blastocoel expansion was graded as A, fully expanded; B, re-expanded; and C, not expanded.

Results: The primary outcome was the clinical pregnancy rate per cycle. In the 134 cycles reviewed, the clinical pregnancy rate (CPR) reached 5.5% of the not expanded; 29.4% of the re-expanded; and 56.92% of the full expanded blastocyst group (p<0.005).

Conclusion: Post-thawed fully expanded blastocysts are associated with a higher clinical pregnancy rate. However, embryos with a poor morphology post-thawed still demonstrate a considerable probability of clinical pregnancy.