Department of Obstetrics and Gynecology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, 123 Ta-Pei Road, Niao-Sung District, Kaohsiung city, Taiwan.
Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Reprod Biol Endocrinol. 2019 Oct 30;17(1):87. doi: 10.1186/s12958-019-0535-2.
Morulas with delayed growth sometimes coexist with blastocysts. There is still limited evidence regarding the optimal disposal of surplus morulas. With the advancement of vitrification, the freezing-thawing technique has been widely applied to zygotes with 2 pronuclei, as well as embryos at the cleavage and blastocyst stages. The freezing of morulas, however, has rarely been discussed. The purpose of this study was to investigate whether these poor-quality and slow-growing morulas are worthy of cryopreservation.
This is a retrospective, observational, proof-of-concept study. A total of 1033 day 5/6 surplus morulas were cryopreserved from January 2015 to December 2018. The study included 167 women undergoing 180 frozen embryo transfer cycles. After the morulas underwent freezing-thawing procedures, their development was monitored for an additional day. The primary outcome was the blastocyst formation rate. Secondary outcomes were clinical pregnancy rate, live birth rate and abortion rate.
A total of 347 surplus morulas were thawed. All studied morulas showed delayed compaction (day 5, n = 329; day 6, n = 18) and were graded as having low (M1, n = 54), medium (M2, n = 138) or high (M3, n = 155) fragmentation. The post-thaw survival rate was 79.3%. After 1 day in extended culture, the blastocyst formation rate was 66.6%, and the top-quality blastocyst formation rate was 23.6%. The day 5 morulas graded as M1, M2, and M3 had blastocyst formation rates of 88.9, 74.0, and 52.8% (p < 0.001), respectively, and the top-quality blastocyst formation rates were 64.8, 25.2, and 9.0% (p < 0.001), respectively. The clinical pregnancy rate was 33.6%.
The post-thaw blastocyst formation rate was satisfactory, with approximately one-half of heavily fragmented morulas (M3) developing into blastocysts. Most of the poor-quality morulas were worth to freeze, with the reasonable goal of obtaining pregnancy and live birth. This alternative strategy may be a feasible approach for coping with poor-quality surplus morulas in non-PGS (preimplantation genetic screening) cycles.
发育迟缓的桑椹胚有时与囊胚共存。对于多余桑椹胚的最佳处理方法，仍缺乏有限的证据。随着玻璃化技术的进步，冷冻-解冻技术已广泛应用于具有 2 个原核的受精卵以及卵裂期和囊胚期胚胎。然而，桑椹胚的冷冻保存却很少被讨论。本研究旨在探讨这些质量差、生长缓慢的桑椹胚是否值得冷冻保存。
这是一项回顾性、观察性、概念验证研究。2015 年 1 月至 2018 年 12 月，共有 1033 枚第 5/6 天的多余桑椹胚进行了冷冻保存。该研究纳入了 167 名接受 180 个冷冻胚胎移植周期的妇女。桑椹胚冷冻解冻后，再额外培养一天，监测其发育情况。主要结局是囊胚形成率。次要结局是临床妊娠率、活产率和流产率。
共解冻了 347 枚多余桑椹胚。所有研究的桑椹胚均表现出明显的迟发性致密化（第 5 天，n=329；第 6 天，n=18），且均为低碎片（M1，n=54）、中碎片（M2，n=138）或高碎片（M3，n=155）。解冻后的存活率为 79.3%。在延长培养 1 天后，囊胚形成率为 66.6%，优质囊胚形成率为 23.6%。第 5 天的 M1、M2 和 M3 级桑椹胚的囊胚形成率分别为 88.9%、74.0%和 52.8%（p<0.001），优质囊胚形成率分别为 64.8%、25.2%和 9.0%（p<0.001）。临床妊娠率为 33.6%。
解冻后的囊胚形成率令人满意，约一半碎片严重的桑椹胚（M3）发育为囊胚。大多数质量差的桑椹胚值得冷冻保存，合理的目标是获得妊娠和活产。对于非 PGS（植入前遗传学筛查）周期中的质量差的多余桑椹胚，这种替代策略可能是一种可行的方法。
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