Improving the clinical outcomes by extended culture of day 3 embryos with low blastomere number to blastocyst stage following frozen-thawed embryo transfer

The association between pregnancy outcomes and frozen-thawed embryo transfer cycles based on D3 cell count in high-quality blastocysts

Objective

To investigate the number of cells in D3-stage embryos of high-quality blastocysts as a contributing factor, to evaluate the clinical pregnancy outcomes in frozen-thawed embryo transfer cycles, and to determine the impact of D3-stage cell count on pregnancy outcomes.

Methods

Patients under 38 years old who underwent frozen-thawed single high-quality blastocyst transfer at our center were selected. Based on the cell count of D3 cleavage-stage embryos forming blastocysts, patients were divided into three groups: ≤6 cells, 7-9 cells, and ≥10 cells. A multivariate regression analysis was used to establish the prediction model, analyzing the impact of different D3 cleavage-stage cell counts on clinical pregnancy outcomes to guide clinical laboratories in selecting blastocysts with the best pregnancy outcomes for transfer.

Results

This study identified a significant association between D3 cell count, blastocyst development stage, and embryo age. Embryos with a higher D3 cell count (≥10) were more likely to reach advanced blastocyst stages and form blastocysts by D5, whereas embryos with fewer D3 cells (≤6) were more likely to form blastocysts on D6. While D3 cell count significantly influenced blastocyst stage and timing of embryo development, no significant differences were observed between groups regarding clinical pregnancy, implantation, or live birth rates. Notably, embryos with fewer D3 cells exhibited a significantly lower miscarriage rate than other groups. Multivariate regression analysis showed a significant correlation between blastocyst stage, embryo age, and D3 cell count, particularly in D5 embryos and more advanced blastocysts. The increased miscarriage rate may be related to lower D3 cell count, and inadequate endometrial preparation was associated with poorer pregnancy outcomes. The type of infertility was also linked to D3 cell count, with secondary infertility patients showing more significant influencing factors.

Conclusion

D3 cell count and related factors play a critical role in pregnancy outcomes during frozen-thawed high-quality blastocyst transfer cycles. Optimizing embryo age, selecting blastocysts at different stages, and refining endometrial preparation protocols are likely to enhance clinical pregnancy and live birth rates.

Should we should consider day 3 blastomere number during single vitrified-warmed blastocyst transfer cycle? A retrospective study

The present study investigated whether day 3 blastomere number has an effect on the clinical outcomes during single vitrified-warmed blastocyst transfer cycles. A total of 3294 vitrified-warmed single day 5 blastocyst transferred cycles were analyzed in this retrospective study from January 2018 to December 2021. The cycles were divided into ≥ 7 and < 7 blastomere groups depending on the day 3 embryo blastomere number. The clinical outcomes were compared between the two groups, moreover multivariate logistic regression analysis was conducted to investigate the correlation between the number of day 3 blastomeres and clinical outcomes. The chi-square test demonstrated that the rates of clinical pregnancy and live birth were significantly higher in the ≥ 7 blastomere group compared to the < 7 blastomere group with respect to single high-quality blastocyst transfer cycles. Conversely, these rates were similar in the two groups with respect to single low-quality blastocyst transfer cycles. These results were confirmed by multivariate logistic regression analysis. However, the miscarriage rate was higher in the < 7 blastomere group than in ≥ 7 group during low-quality blastocyst transfer cycles. These results suggested that day 3 blastomere number should be considered during single vitrified-warmed blastocyst transfer cycles. Thus, blastocsyts derived from ≥ 7 blastomere embryos are preferred when choosing the same quality blastocysts.

The optimal frozen embryo transfer strategy for the recurrent implantation failure patient without blastocyst freezing: thawing day 3 embryos and culturing to day 5 blastocysts

This study aimed to investigate the optimal frozen embryo transfer (FET) strategy for recurrent implantation failure (RIF) patients with three consecutive failed cleaved embryo implantations and no blastocyst preservation. This retrospective analysis was divided into three groups based on the FET strategy: thawed day 3 embryo transfer (D3 FET group); and extended culture of frozen-thawed day 3 embryos to day 5 blastocysts transfer (D3-D5 FET group); thawed blastocyst transfer (D5 FET group). Transplant cycle data were compared between the three groups. In total, 43.8% of vitrified-thawed cleavage embryos developed into blastocysts. Analysis of the three transplantation strategies showed that, compared with the D3 FET group, D3-D5 had a significantly better hCG-positivity rate and live-birth rate (P < 0.05). Pregnancy outcomes in the D3-D5 FET group and D5 FET group were similar regarding hCG-positivity rate, implantation rate, clinical pregnancy rate, and live-birth rate. Our findings propose two potentially valuable transfer strategies for patients experiencing repeated implantation failures. The D3-D5 FET approach presents a greater potential for selecting promising embryos in cases without blastocyst preservation; however, this strategy does entail the risk of cycle cancellation. Conversely, in instances where blastocyst preservation is an option, prioritizing consideration of the D5 FET strategy is recommended.

The effect of the day 3 embryo cell number on the neonatal outcomes of day 5 single blastocyst transfer in frozen embryo transfer cycles

OBJECTIVE

To evaluate the influence of the day 3 embryo cell number on the neonatal outcomes of day 5 single blastocyst transfer in frozen embryo transfer (FET) cycles.

METHODS

This retrospective study analysed a total of 2315 delivery cycles of day 5 single blastocyst transfer in FET cycles, including 489, 761 and 1103 live-born infants segregated according to a day 3 embryo cell number of <8, 8 and >8 cells, respectively. The neonatal outcomes of the three groups were compared.

RESULTS

The day 3 embryo cell number did not significantly affect the incidence of monozygotic twins. The sex ratio increased as the day 3 embryo cell number increased, but the difference was not statistically significant. There were no significant differences in the rates of preterm birth or low birth weight among the three groups. The rates of stillbirths and neonatal deaths were also not significantly different among the three groups. Moreover, the day 3 embryo cell number did not increase the risk of birth defects in newborns.

CONCLUSIONS

The day 3 embryo cell number did not significantly affect neonatal outcomes.

The influence of day 3 embryo cell number on the clinical pregnancy and live birth rates of day 5 single blastocyst transfer from frozen embryo transfer cycles

BACKGROUND

To evaluate the influence of day 3 embryo cell number on the clinical pregnancy and live birth rates of day 5 single blastocyst transfer in frozen embryo transfer (FET) cycles.

METHODS

Our retrospective study included 3761 day 5 single blastocyst FET cycles between January 2015 and December 2019. These FET cycles were divided into three groups according to the day 3 embryo cell number: 939 cycles in the < 8-cell group, 1224 cycles in the 8-cell group and 1598 cycles in the > 8-cell group. The clinical pregnancy and live birth rates were compared among the three groups.

RESULTS

The clinical pregnancy rate of day 5 single blastocyst transfer in FET cycles increased significantly as the day 3 embryo cell number increased (52.2%, 61.4% and 66.8%, P < 0.001). Similarly, the live birth rate increased significantly as the day 3 embryo cell number increased (42.7%, 49.8% and 54.9%, P < 0.001). The results of the subgroup analysis showed that the clinical pregnancy and live birth rates were not significantly different among the three groups when good-quality blastocysts were transferred. The clinical pregnancy and live birth rates increased significantly as the day 3 embryo cell number increased when fair- and poor-quality blastocysts were transferred.

CONCLUSION

The day 3 embryo cell number needs to be considered when day 5 single blastocyst transfer is performed in FET cycles, especially when fair- and poor-quality blastocysts are used for transfer. The transfer of a day 5 single blastocyst derived from an embryo with faster development on day 3 may shorten the time to achieving a live birth.

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.