High three pro-nuclei (3PN) zygotes proportion associated with normal embryo multinucleation at the two-cell stage: two cases report

Abstract

Objective: Blastomere multinucleation at the two-cell stage (MN2) is a common nuclear abnormality observed in early human embryos and known to decrease the implantation rate. The aim of this study is to explore whether or not there is a link between high 3PN zygotes proportion and MN2 incidence.

Methods: For embryo culture in the conventional incubator, the evaluation of nuclear status of two-cell stage is usually not performed. Therefore, the MN2 phenomenon is easily ignored. The time-lapse monitoring system (TLS) offers a promising new method to evaluate embryo development. We reported two cases who had single 2PN zygote and more than four 3PN zygotes in the conventional in-vitro fertilization (c-IVF) cycle.

Results: We observed the MN2 incidence in the single normal embryo by TLS which suggested that it might be resulted from high 3PN zygotes proportion incidence. No available embryo was obtained in the first c-IVF cycle and the intracytoplasmic sperm injection (ICSI) treatment was performed in the second cycle. In subsequent ICSI cycles, we observed no 3PN zygotes incidence and transferred two day 3 embryos for the patients. Finally, the two couples successfully obtained healthy babies.

Conclusions: High 3PN zygotes proportion might be associated with the MN2 incidence.

摘要

目的：两细胞阶段的卵裂球多核化 (MN2) 是人类早期胚胎常见的核异常, 可降低着床率。本研究的目的是探讨高比例的3PN受精卵与MN2发病率之间是否存在联系。

方法：对于常规培养箱中的胚胎培养, 通常不进行两细胞阶段的核状态评估。因此, MN2现象很容易被忽略。延时监视系统 (TLS) 提供了一种有前途的评估胚胎发育的新方法。我们报道了两个在常规体外受精 (c-IVF) 周期中具有单个2PN受精卵和四个以上3PN受精卵的病例。

结果：我们通过TLS观察到单个正常胚胎中MN2的发生率, 这表明它可能是3PN受精卵比例较高所致。第一个c-IVF周期未获得可用胚胎, 第二个周期进行了卵胞浆内单精子注射 (ICSI)。在随后的ICSI周期中, 我们没有观察到3PN受精卵的发生, 并为患者移植了两个第3天的胚胎。最终, 这两对夫妇成功获得了健康的婴儿。

结论:高比例的3PN受精卵可能与MN2的发生有关。

Keywords:

• Blastomere multinucleation
• three pro-nuclei
• time-lapse

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This project was supported by Shaanxi Technology Committee Industrial Public Relation Project (Project Number: 2018SF-260).