# Clinical Insights Regarding the Targeted Chromosomal Region for Mosaicism and Aneuploidy in Embryos in IVF Treatment and Literature Review

## TL;DR

This study identifies specific chromosomal regions linked to mosaicism and aneuploidy in IVF embryos, aiming to improve embryo selection and genetic counseling.

## Contribution

The study reveals distinct chromosomal regions predominantly affected by mosaicism and aneuploidy in IVF embryos.

## Key findings

- Mosaicism primarily affects chromosomes 1–9, especially chromosomes 1, 7, and 9.
- Aneuploidy mainly targets chromosomes 16–22, particularly chromosomes 16, 19, and 22.
- Mosaicism and aneuploidy show uneven genomic distribution, suggesting targeted chromosomal regions.

## Abstract

Background: Given the common occurrence of mosaicism and aneuploidy in IVF embryos, our study aimed to retrospectively identify whether specific chromosomal regions or individual chromosomes are predominantly affected in our clinic. Understanding these patterns can improve embryo selection, reduce miscarriage risks, and enhance genetic counseling. At the same time, due to the limited data on potential comorbidities in affected children, our findings aim to support both clinicians and patients in making informed decisions. Methods: The retrospective clinical study included 461 PGT-A biopsies from our clinic database (September 2023–December 2024) to determine whether specific chromosome regions or individual chromosomes (C) are more likely to be mosaic or aneuploid. Results: Among the 461 embryos analyzed in our clinic, the incidence rate of mosaicism was 16.70% whereas the aneuploidy rate was 32.10%. Our results showed that mosaicism tends to target a specific chromosomal region in embryos, namely the chromosome 1 to 9 region, in particular chromosomes 7, 1, 9. On the other hand, aneuploidy targets the chromosomal region chromosome 16 to 22, particularly chromosomes 16, 19, and 22. Conclusions: Our data suggest that mosaicism and aneuploidy affect the genome in an uneven manner and are often concentrated in specific chromosomal regions, with mosaicism primarily affecting the C1–C9 region and aneuploidy targeting the C16–C22 region. These data highlight the need for further research to understand these patterns and the impact of IVF methods on chromosomal targeting. Comparative studies could also be helpful in genetic counseling by clarifying the implications of the levels of mosaicism in the newborn.