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

Abstract

Purpose This study aimed to investigate whether the extended culture of day 3 (D3) embryos with low blastomere number to blastocyst following frozen–thawed embryo transfer improved the clinical outcomes. Methods This was a retrospective study of clinical data of women undergoing in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles in the Tangdu Hospital. The patients were divided into groups with 4–5, 6, 7–9 and > 9 cells based on the blastomere number of D3 embryos. The clinical outcomes were compared. Results In fresh transfer cycles, the implantation and clinical pregnancy rates significantly decreased, while the abortion rate significantly increased in the groups with 4–5 and 6 cells compared with those with 7–9 and > 9 cells. In frozen–thawed transfer cycles, the clinical pregnancy and implantation rates for a single blastocyst transfer cycle showed no significant differences in the groups with 4–5 and 6 cells compared with those with 7–9 and > 9 cells. However, the abortion rate was significantly higher in the group with 4–5 cells than in that with 7–9 and > 9 cells. In the double blastocyst transfer cycle, the clinical pregnancy rate showed no significant differences among the groups with 4–5, 6, and 7–9 cells. Conclusion The implantation and clinical pregnancy rates of D3 embryos with 6 cells significantly decreased; these embryos were not considered as high-quality embryos. Extended culture of D3 embryos with ≤ 6 blastomeres to blastocysts, particularly 6-cell embryos, resulted in a similar clinical pregnancy rate as that of blastocysts derived from D3 embryos with ≥ 7 blastomeres.

The effects of different post-thawed culture periods on clinical outcomes in frozen embryo transfer cycle: a retrospective study

“…7 blastomeres. 12 The CPR, IR, and LBR were similar in the elective single morula embryo transfer group and elective single blastocyst embryo transfer group. 21,22 A trend toward higher clinical and ongoing pregnancy rates was noted after day 4 embryo transfers when compared with day 3 embryos in ET cycles.…”

“…6 blastomeres were associated with low IR, CPR, and LBR and high AR compared with those with > 6 blastomeres. 10,12,16 So, the quality of transferred embryos may be another factor contributing to the discrepancy in different studies. One limitation of this study was that patients' characteristic of the number of oocytes from the OPU was not mentioned.…”

“…8,9 Currently, the two most common procedures to select embryos for FET differ in the duration of the postthawed culture: one relies upon the observation of blastomere survival after thawing, requiring a short culture; another is dependent on the observation of blastomere proliferation, requiring a long culture, generally overnight. Some studies indicated that cleavage stage embryos with low blastomere number had significantly decreased developmental potential and pregnancy rate, [10][11][12] and extended culture of these embryos to blastocysts can resulted in a similar clinical pregnancy rate as that of blastocysts derived from embryos with [?] 7 blastomeres.…”

“…7 blastomeres. 12,13 The influence of post-thawed culture for about 18 h on the outcome of FET is still controversial, 12,14,15 and the reasons may be related to the different sample sizes, inclusion criteria, embryo freezing methods, embryo quality and age distribution of patients in different studies. Previous studies focused on the comparison between short culture and long culture, while ignoring the effect of age and embryo quality on implantation and live birth rates.…”

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

“…The studies mentioned above all focused on the effect of the transfer of cleavage-stage embryos with different cell numbers on the clinical outcomes. Li et al [7] found that the implantation and clinical pregnancy rates of ≤6-cell embryos were signi cantly lower than those of 7-9-cell and >9-cell embryos in fresh transfer cycles. However, the implantation and clinical pregnancy rates were no signi cant differences in single blastocyst transfer of ≤6-cell embryos compared with that of ≥7-cell embryos in frozen embryo transfer (FET) cycles.…”