Morula transfer achieves better clinical outcomes than post-thawed cleavage embryos after overnight culture in frozen embryo transfer (FET) cycles

Altered morphokinetics and differential reproductive outcomes associated with cell exclusion events in human embryos

RESEARCH QUESTION

Can embryos harbouring cell exclusion and their reproductive outcomes be classified based on morphokinetic profiles?

DESIGN

A total of 469 time-lapse videos of embryos transferred between 2013 and 2019 from a single clinic were analysed. Videos were assessed and grouped according to the presence or absence of one or more excluded cells before compaction. Cell division timings, intervals between subsequent cell divisions and dynamic intervals were analysed to determine the morphokinetic profiles of embryos with cell exclusion (CE+), compared with fully compacted embryos without cell exclusion or extrusion (CE-).

RESULTS

Transfer of CE+ embryos resulted in lower proportions of fetal heartbeat (FHB) and live birth compared with CE- embryos (both, P < 0.001). CE+ embryos were associated with delays in t2 (P = 0.030), t6 (P = 0.018), t7 (P < 0.001), t8 (P = 0.001), tSC (P < 0.001) and tM (P < 0.001). Earlier timings for t3 (P = 0.014) and t5 (P < 0.001) were positively associated with CE+; CE+ embryos indicated prolonged S2, S3, ECC3, cc2 and cc4. Logistic regression analysis revealed that t5, tM, S2 and ECC3 were the strongest predictive indicators of cell exclusion. Timings for S2 and ECC3 were useful in identifying increased odds of FHB when a cell exclusion event was present.

CONCLUSION

Embryos harbouring cell exclusion indicated altered morphokinetic profiles. Their overall lower reproductive success was associated with two morphokinetic parameters. Morphokinetic profiles could be used as adjunct indicators for reproductive success during cycles producing few, low-quality embryos. This may allow more objective identification of cell exclusion and refinement of embryo ranking procedures before transfer.

Impact of Post-Thaw Incubation Time of Frozen Embryos on Clinical Pregnancy Rate

Background

Vitrification of embryos following a single-controlled ovarian stimulation has been the strategy practised now in many in vitro fertilisation clinics to minimise the risk of early ovarian hyper stimulation syndrome, to reduce multiple pregnancy rates and to improve cumulative pregnancy rates. In recent years, advances in vitrification techniques and improved culture conditions have led to good post-thaw embryo survival rates, thereby increasing pregnancy rates of frozen embryo transfer (FET) cycles.

Aim

The aim of this study was to analyse the effect of post-thaw incubation time of frozen embryos on the clinical pregnancy rates (CPRs) of frozen embryo transfer (FET) cycles.

Settings and Design

This was a retrospective, comparative study done at a teaching hospital in assisted reproductive treatment.

Materials and Methods

Three hundred and ten FET cycles were analysed, of which 125 had day 2 freezing and 185 had day 3 freezing. Depending upon the day of thawing and day of transfer, FET cycles were divided into six groups: Group 1 (day 2 thawing and day 3 transfer), Group 2 (day 2 thawing and day 4 transfer), Group 3 (day 2 thawing and day 5 transfer), Group 4 (day 3 thawing and day 3 transfer), Group 5 (day 3 thawing and day 4 transfer) and Group 6 (day 3 thawing and day 5 transfer).

Statistical Analysis Used

Statistical analysis was performed using version 14 R software version 4.0.1 (2020-06-06) (R foundation for Statistical Computing, Vienna, Austria). A P < 0.05 is taken as significant.

Results

The CPR of Group 4 was 42.4% which was more than that of the other groups but it did not reach statistical significance.

Conclusions

Short incubation time of 2-4 h is as effective as an extended incubation time in terms of CPRs of FET cycles.

Clinical Outcome of Day-3 Cleavage Slow-Growing Embryos at Different Cleavage Rates after Overnight Culture: A Cohort Retrospective Study

INTRODUCTION

We explored the association between clinical outcomes and the cleavage rate of day-3 cleavage slow-growing embryos after overnight culture.

METHODS

The data collected from 303 frozen embryo transfer (FET) cycles with 606 4-cell or 5-cell embryos cultured overnight (18-22 h) after thawing were analyzed. Based on the growth rate after the overnight culture, the embryos were divided into three groups: no embryo reaching eight cells (Group I), either one of the two embryos reaching eight cells (Group II), and both two embryos reaching eight cells or more (Group III). A statistical analysis of the different clinical outcomes from the three groups was performed.

RESULTS

Biochemical pregnancy rate (OR 3.22; p = 0.001), implantation rate (OR 2.44; p = 0.002), clinical pregnancy rate (OR 3.04; p = 0.001), ongoing pregnancy rate (OR 3.14; p = 0.001), and live birth rate (OR 2.78; p = 0.004) were significantly higher in Group III as compared to Group I. Group II had a significantly higher biochemical pregnancy rate (OR 2.02; p = 0.013) and implantation rate (OR 1.77; p = 0.019) than Group I.

CONCLUSIONS

The capability of day-3 cleavage slow-growing embryos to reach eight cells, especially that of two embryos reaching eight cells by overnight culture, appear to result in a better pregnancy outcome.

The Effects of Different Post-thawed Culture Periods on Clinical Outcomes in Frozen Embryo Transfer Cycle

The purpose of this study is to evaluate the effects of different post-thawed culture periods on the clinical outcomes. 9381 frozen embryo transfer (FET) cycles were divided into three groups according to female age: < 35, 35-39, and > 39 years, and two groups depending on post-thawed culture period before transfer: short culture (2-3 h) group (S) and long culture (18-20 h) group (L). According to the increment number of post-thawed embryos, the L group divided into three groups: ≤ 2, one ≤ 2 and the other > 2, and > 2 groups. Pregnancy outcomes included the implantation rate (IR), clinical pregnancy rate (CPR), multiple pregnancy rate (MPR), live birth rate (LBR), and neonatal characteristics. Long post-thawed culture caused a significant increase in the IR, CPR, MPR, and LBR (p = 0.000, 0.004, 0.037, and 0.001; CI = 1.06-1.194, 1.042-1.237, 1.008-1.254, and 1.054-1.245, respectively), and blastomere increment number also had a significant effect on IR, CPR, MPR, and LBR (p = 0.000, 0.000, 0.000, and 0.000, respectively). No significant differences were present in neonatal characteristics between the two post-thawed culture groups. Singleton group had a higher average gestational age and birthweight as well as a lower cesarean section rate, preterm labor rate, and low birthweight rate than twins group. Long post-thawed culture was associated with higher IR, CPR, MPR, and LBR, and transferring a well-developed embryo after long post-thawed culture might be a viable embryo transfer strategy to decrease MPR while maintaining CPR and LBR.