Talbot Anna L, Alexopoulou Evaggelia, Kallemose Thomas, Freiesleben Nina la Cour, Nielsen Henriette S, Zedeler Anne
Department of Obstetrics and Gynecology, The Fertility Clinic, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark.
The Fertility Clinic, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
Hum Reprod Open. 2022 Nov 24;2022(4):hoac049. doi: 10.1093/hropen/hoac049. eCollection 2022.
How does nucleus status at the two-cell stage predict blastocysts formation and clinical outcome after single blastocyst transfer?
Binucleated embryos at the two-cell stage (2BI) show higher rates of good quality blastocyst formation, pregnancy and live birth compared to those with one nucleus in each blastomere (2MONO), whereas true multinucleated embryos at the two-cell stage (2MULTI) show lower rates of good quality blastocyst formation and pregnancy compared to 2MONO embryos.
The introduction of time-lapse culture has made it possible to study nucleus status at the two-cell stage more consistently and it shows that multinucleation at the two-cell stage (2MN) is a common event. The effect of 2MN is still unclear. High numbers of 2MN with the potential to develop to blastocysts that become clinical pregnancies and result in birth of healthy babies with no impaired perinatal outcome have been reported. However, some studies have found 2MN to be associated with impaired implantation and live birth. Furthermore, knowledge on how the different subgroups of multinucleation affects the IVF outcome is limited.
A non-interventional retrospective study was performed in a public fertility clinic. Blastocyst formation data from 223 women attending their first IVF cycle between May 2016 and December 2018, and clinical outcome data from 1314 single blastocyst transfers between May 2014 and December 2018 were used for the study. Fresh and frozen-thawed embryo transfers were included.
PARTICIPANTS/MATERIALS SETTING METHODS: Embryos were cultured until the blastocyst stage in a time-lapse incubator and nucleus status at the two-cell stage, the Gardner score and other morphokinetic parameters were annotated. We compared blastocyst development and clinical outcome, including positive hCG, ongoing pregnancy and live birth, of embryos with 2BI and/or 2MULTI blastomeres to 2MONO embryos.
Embryos with 2BI in one blastomere (2BI1) were twice as likely to develop to good quality blastocysts (odds ratio (OR) 2.54, 95% CI 1.30-4.95, = 0.006) compared to 2MONO embryos. Embryos with 2MULTI in both blastomeres (2MULTI2) were significantly less able to develop to good quality blastocysts (OR 0.38, 95% CI 0.23-0.63, < 0.001) compared to 2MONO embryos. Embryos with 2BI in both blastomeres (2BI2) had a significantly better chance of resulting in a positive hCG (OR 2.40, 95% CI 1.11-5.20, = 0.027), ongoing pregnancy (OR 2.79, 95% CI 1.29-6.04, = 0.009) and live birth (OR 3.16, 95% CI 1.43-6.95, = 0.004) compared to 2MONO blastocysts after single blastocyst transfer. In contrast, 2MULTI2 embryos were significantly less likely to result in a positive hCG (OR 0.58, 95% CI 0.35-0.97, = 0.036) and ongoing pregnancy (OR 0.51, 95% CI 0.28-0.94, = 0.030) compared to 2MONO blastocysts.
Discrepancies among the existing studies regarding the definition of multinucleation may lead to different conclusions. Even though the distinction between binucleation and true multinucleation was a strength in our study design, a further distinction between true multinucleated and micronucleated embryos could be interesting to investigate in future studies. Also, we included any anucleated embryos in the 2MONO group. For the study of clinical outcomes, the patients were allowed to be included with more than one transfer cycle. Both fresh and thawed transfers were included.
We find it important to discriminate between binucleation and true multinucleation when evaluating embryo nucleus status at the two-cell stage. Embryos displaying 2BI1 and 2BI2 have significantly better good quality blastocyst formation rates and clinical outcome after single blastocyst transfers, respectively. 2MULTI2 embryos have impaired blastocyst development potential and poorer clinical outcomes.
STUDY FUNDING/COMPETING INTERESTS: H.S.N. received an unrestricted grant from Merck for 3 months' normal salary for a medical Doctor (A.L.T.) to write the manuscript. Merck was not involved in the study design, analysis, interpretation of data, writing the paper or the decision to submit the manuscript for publication. H.S.N. has received speaker's fees from Ferring Pharmaceuticals, Merck Denmark A/S, Astra Zeneca, Cook Medical and Ibsa Nordic (outside the submitted work). N.l.C.F. has received a grant from Gedeon Richter (outside the submitted work). The other authors did not report any potential conflicts of interest. All authors declared no conflicts of interest regarding this work.
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二细胞期的细胞核状态如何预测单囊胚移植后的囊胚形成及临床结局？
与每个卵裂球含一个细胞核的二细胞期胚胎（2MONO）相比，二细胞期双核胚胎（2BI）形成优质囊胚、妊娠及活产的比率更高；而二细胞期真正的多核胚胎（2MULTI）与2MONO胚胎相比，形成优质囊胚及妊娠的比率更低。
延时培养技术的引入使人们能够更连贯地研究二细胞期的细胞核状态，且研究表明二细胞期多核化（2MN）是一种常见现象。2MN的影响尚不清楚。有报道称，大量具有发育为囊胚潜力的2MN胚胎可实现临床妊娠，并产下健康婴儿，围产期结局无不良影响。然而，一些研究发现2MN与着床及活产受损有关。此外，关于多核化的不同亚组如何影响体外受精结局的知识有限。
研究设计、规模、持续时间：在一家公立生育诊所进行了一项非干预性回顾性研究。研究使用了2016年5月至2018年12月期间接受首次体外受精周期的223名女性的囊胚形成数据，以及2014年5月至2018年12月期间1314次单囊胚移植的临床结局数据。包括新鲜胚胎移植和冻融胚胎移植。
研究对象/材料、研究环境、方法：胚胎在延时培养箱中培养至囊胚期，并记录二细胞期的细胞核状态、Gardner评分及其他形态动力学参数。我们比较了具有2BI和/或2MULTI卵裂球的胚胎与2MONO胚胎的囊胚发育及临床结局，包括hCG阳性、持续妊娠和活产情况。
与2MONO胚胎相比，一个卵裂球为2BI的胚胎（2BI1）发育为优质囊胚的可能性是其两倍（优势比（OR）2.54，95%置信区间1.30 - 4.95，P = 0.006）。与2MONO胚胎相比，两个卵裂球均为2MULTI的胚胎（2MULTI2）发育为优质囊胚的能力明显更低（OR 0.38，95%置信区间0.23 - 0.63，P < 0.001）。与单囊胚移植后的2MONO囊胚相比，两个卵裂球均为2BI的胚胎（2BI2）出现hCG阳性（OR 2.40，95%置信区间1.11 - 5.20，P = 0.027）、持续妊娠（OR 2.79，95%置信区间1.29 - 6.04，P = 0.009）和活产（OR 3.16，95%置信区间1.43 - 6.95，P = 0.004）的可能性明显更高。相比之下，与2MONO囊胚相比，2MULTI2胚胎出现hCG阳性（OR 0.58，95%置信区间0.35 - 0.97，P = 0.036）和持续妊娠（OR 0.51，95%置信区间0.28 - 0.9
