Background:We aimed to assess whether the survival rate of embryos is influenced by the number of embryos/oocytes loaded on a single cryo-carrier during vitrification.Methods:This was a retrospective study that included 974 patients who underwent thawing of 1896 embryo-warming cycles between September 2016 and January 2020. A distinct analysis was made for cleavage stage embryos (2–10-cell stage) and blastocysts. For vitrification, embryos were placed in a Cryotop™ open device using a SAGE vitrification kit following the manufacturer’s instructions. Warming was carried using a SAGE warming vitrification kit according the manufacturer’s instructions.Results:Total post-vitrification survival rates of embryos at the cleavage stage or blastocyst stage was 94.8%. At the cleavage stage, cryo-preserving three embryos per single cryo-carrier gave the highest full intact embryo survival rate (91.5%) compared with one or two embryo(s) per single cryo-carrier (85.7%, P < 0.0002 and 87.3%, P < 0.004). Conversely, post warmed full intact blastocyst survival rate for two blastocysts was significantly lower compared with one blastocyst (76.7% vs. 87.9%, P < 0.0193) per single cryo-carrier.Conclusion:Post-thawing survival rate following vitrification is affected by the number of embryos per single cryo-carrier undergoing the vitrification equilibration phase, with the optimum number of three cleaved embryos or one blastocyst per single cryo-carrier. Further studies are required to determine the optimum number of cleaved embryos or blastocysts that should be loaded onto a single cryo-carrier vitrification device.

中文翻译：

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装载在单个冷冻载体上的胚胎数量是否会影响玻璃化后的存活率？

背景：我们旨在评估胚胎的存活率是否受玻璃化冷冻期间装载在单个冷冻载体上的胚胎/卵母细胞数量的影响。方法：这是一项回顾性研究，包括 974 名接受 1896 胚胎加热解冻的患者周期在 2016 年 9 月至 2020 年 1 月之间。对卵裂期胚胎（2-10 细胞期）和囊胚进行了不同的分析。对于玻璃化，按照制造商的说明，使用 SAGE 玻璃化试剂盒将胚胎置于 Cryotop™ 开放式装置中。加温采用SAGE加温玻璃化试剂盒，按照厂家说明进行。结果：卵裂期或囊胚期胚胎玻璃化冷冻后总成活率为94.8%。在分裂阶段，磷< 0.0002 和 87.3%，磷< 0.004)。相反，两个囊胚的加热后完整完整囊胚存活率显着低于一个囊胚（76.7% vs. 87.9%，磷< 0.0193)/单个冷冻载体。结论：玻璃化冷冻后的解冻后存活率受处于玻璃化平衡阶段的每个冷冻载体的胚胎数量影响，每个冷冻载体的最佳数量为三个切割胚胎或一个囊胚-载体。需要进一步的研究来确定应该装载到单个冷冻载体玻璃化装置上的切割胚胎或囊胚的最佳数量。