Chromosomal mosaicism detected during preimplantation genetic testing for aneuploidy (PGT-A) and its impact on embryo implantation have been widely discussed, and healthy live births from mosaic embryos were reported by many groups. On the other hand, only very few studies have focused on segmental chromosome aneuploidies and their clinical impact. Eighty-nine embryos with various PGT-A results (trophectoderm 1: TE1) were re-analysed using a second trophectoderm biopsy (TE2) and the rest of the embryo (RE) for testing. Of 19 euploid TE1 biopsies, 18 were concordant across TE2 and RE. Similarly, whole chromosomal aneuploidies were concordant in 59 of 62 TE1-TE2 and 58 TE1-RE. In contrast, from 31 segmental aneuploidies detected in TE1, only 15 were observed again in TE2 and 14 in RE. If a TE1 segmental abnormality appeared again in TE2, it was almost always present in RE (17/18) as well. Moreover, when a TE1 segmental abnormality was not detected in TE2, in 12 out of 13 cases RE was also unaffected. Similarly, only 1 of 26 TE1 whole chromosome mosaics were repeated in TE2 and 7 in RE. Our study confirms that euploid and whole chromosomal aneuploidy results are highly predictive of the embryo. In contrast, mosaicism has a very low concordance rate. Most importantly, re-biopsy of embryos with segmental aneuploidies demonstrated that they are mostly not uniform across the embryo. Finally, in the case of segmental aneuploidy, the second biopsy enables an accurate prediction of the real status of the embryo and could be offered to patients undergoing PGT-A.

中文翻译：

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胚胎不同部分之间各种染色体错误的一致性以及节段性非整倍体胚胎重新活检的价值。

在植入前非整倍体基因检测（PGT-A）过程中检测到的染色体嵌合现象及其对胚胎植入的影响已被广泛讨论，并且许多团体报告了嵌合胚胎的健康活产。另一方面，只有很少的研究关注节段染色体非整倍体及其临床影响。使用第二次滋养外胚层活检 (TE2) 和胚胎的其余部分 (RE) 重新分析具有不同 PGT-A 结果的 89 个胚胎（滋养外胚层 1：TE1）并进行测试。在 19 个整倍体 TE1 活检中，18 个在 TE2 和 RE 上是一致的。同样，62 个 TE1-TE2 中的 59 个和 58 个 TE1-RE 中的全染色体非整倍体是一致的。相比之下，在 TE1 中检测到的 31 个节段非整倍体中，在 TE2 中仅再次观察到 15 个，在 RE 中仅观察到 14 个。如果 TE1 节段异常再次出现在 TE2 中，则它几乎也总是出现在 RE 中 (17/18)。此外，当在 TE2 中未检测到 TE1 节段异常时，13 例中有 12 例 RE 也不受影响。同样，26 个 TE1 全染色体嵌合体中只有 1 个在 TE2 中重复，7 个在 RE 中重复。我们的研究证实，整倍体和全染色体非整倍体结果可以高度预测胚胎。相比之下，镶嵌现象的一致率非常低。最重要的是，对具有节段性非整倍性的胚胎进行重新活检表明，它们在整个胚胎中大多不一致。最后，在节段性非整倍体的情况下，第二次活检能够准确预测胚胎的真实状态，并可以提供给接受 PGT-A 的患者。