European Society of Human Reproduction and Embryology (ESHRE) 34th Annual Meeting
当院参加： 胚培養士 2名
<Effectiveness of ≥170-μm diameter criterion for blastocyst cryopreservation>
Does setting a ≥170-μm diameter criterion for blastocyst cryopreservation influence clinical outcomes following implantation of frozen-thawed embryos?
Pregnancy rates following frozen-thawed embryo transfer were constant, irrespective of blastocyst diameter.
What is known already:
Frozen blastocyst transfer is known to yield higher pregnancy rates than fresh blastocyst transfer due to embryo-endometrium synchronization.We previously froze good-quality blastocysts at stage 3, and then thawed them on the day before transfer. Blastocysts were developed to stage 4 on the following day and then implanted, and we reported a resultant improvement in post-freeze-thaw pregnancy rate over thawing on the day of transfer.Based on this, we changed our cryopreservation criterion to stage 4 (blastocyst diameter ≥170 μm) in 2017.
Study design, size, duration:
We targeted 547 cycles subject to single frozen-thawed blastocyst transfer between January and October 2017 for analysis in this study. Only good-quality blastocysts with diameter ≥170 μm at days 5 and 6 were eligible for analysis. Blastocyst diameter was measured from images taken immediately prior to cryopreservation, using an EmbryoScope system.
Participants/materials, setting, methods:
Blastocysts were classified by diameter into Categories A (170 to 179 μm), B (180 to 189 μm), C (190 to 199 μm), and D (≥ 200). We compared pregnancy rates between the four blastocyst categories after 5- and 6-day incubation periods.
Main results and the role of chance:
Pregnancy rates achieved with transferred blastocysts after 5-day incubation showed no significant differences between the 4 diameter categories, at 41.8% (64/153) for Category A, 39.5% (45/114) for Category B, 47.6% (30/63) for Category C, and 41.6% (32/77) for Category D. Pregnancy rates achieved with transferred blastocysts after 6-day incubation showed no significant differences between the 4 diameter categories, at 29.5% (13/44) in Category A, 21.4% (9/42) in Category B, 45.5% (10/22) in Category C, and 46.9% (15/32) in Category D; however, the rates in Categories C and D tended to be high.
Limitations, reasons for caution:
This study is limited to its retrospective design and small sample size.
Wider implications of the findings:
Pregnancy rates showed no significant difference between transferred blastocyst categories irrespective of incubation periods; therefore, we considered that the cryopreservation criterion setting investigated in this study did not influence pregnancy outcome. Accordingly, we suggest that a criterion of diameter ≥170 μm is effective for blastocyst cryopreservation.