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Background <p>Early pregnancy loss is frequently associated with fetal chromosomal abnormalities, trisomy being the most common cause, especially during the first trimester. A notable phenomenon in such cases is trisomy rescue where the loss of an extra chromosome during mitotic division can result in mosaicism, a condition characterized by the presence of genetically distinct cell populations within the same embryo. Trisomy rescue may occur in more than one chromosome, a rare phenomenon known as double trisomy rescue. On the other hand, parallel rescue is a process where, if a trisomic zygote carries an abnormal chromosome, it must be corrected twice in parallel, losing the normal and the abnormal chromosomes separately. Taken together, these complex and rare phenomena highlight the fact that cellular rescue mechanisms in aneuploid cell divisions remain poorly understood and challenging to characterize, particularly given the high rate of mitotic errors during early embryogenesis.</p> Case presentation <p>A couple underwent in vitro fertilization (IVF) and the pregnancy ended at 8 weeks of gestation due to spontaneous loss of fetal cardiac activity. Genetic tests revealed a complex mosaic chromosomal profile including both segmental copy number variations (CNV) and whole-chromosome aneuploidies.</p> Conclusion <p>This study investigates the complexity of chromosomal mosaicism in early pregnancy loss, focusing on the potential involvement of both meiotic and postzygotic mitotic errors. This case report aims to identify molecular mechanisms that may underlie combined segmental and whole-chromosome abnormalities in an embryo, thereby enhancing our understanding of molecular mechanisms in early pregnancy loss and its potential implications for clinical outcomes, including implantation failure and miscarriage.</p>

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Identifying a rare mechanism: double parallel trisomy rescue leading to combined segmental and whole-chromosome mosaicism in an IVF-derived embryo

  • 期刊论文

  • 发表日期：

    2025年10月17日

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  • Elif Kubar,
  • Alp Peker,
  • İrem Oflaz,
  • Erhan Parıltay,
  • Aslı Ece Solmaz,
  • Haluk Akın,
  • Emin Karaca

摘要

Background

Early pregnancy loss is frequently associated with fetal chromosomal abnormalities, trisomy being the most common cause, especially during the first trimester. A notable phenomenon in such cases is trisomy rescue where the loss of an extra chromosome during mitotic division can result in mosaicism, a condition characterized by the presence of genetically distinct cell populations within the same embryo. Trisomy rescue may occur in more than one chromosome, a rare phenomenon known as double trisomy rescue. On the other hand, parallel rescue is a process where, if a trisomic zygote carries an abnormal chromosome, it must be corrected twice in parallel, losing the normal and the abnormal chromosomes separately. Taken together, these complex and rare phenomena highlight the fact that cellular rescue mechanisms in aneuploid cell divisions remain poorly understood and challenging to characterize, particularly given the high rate of mitotic errors during early embryogenesis.

Case presentation

A couple underwent in vitro fertilization (IVF) and the pregnancy ended at 8 weeks of gestation due to spontaneous loss of fetal cardiac activity. Genetic tests revealed a complex mosaic chromosomal profile including both segmental copy number variations (CNV) and whole-chromosome aneuploidies.

Conclusion

This study investigates the complexity of chromosomal mosaicism in early pregnancy loss, focusing on the potential involvement of both meiotic and postzygotic mitotic errors. This case report aims to identify molecular mechanisms that may underlie combined segmental and whole-chromosome abnormalities in an embryo, thereby enhancing our understanding of molecular mechanisms in early pregnancy loss and its potential implications for clinical outcomes, including implantation failure and miscarriage.