# Case Report: Discordant genetic findings in miscarriage tissue following transfer of euploid embryos

## TL;DR

This case report describes two instances where pregnancies from euploid embryos still resulted in miscarriage due to genetic issues not detected by preimplantation testing.

## Contribution

The report highlights the limitations of PGT-A in detecting embryonic mosaicism and the need for additional prenatal diagnosis.

## Key findings

- PGT-A-identified euploid embryos can still lead to miscarriage due to undetected chromosomal abnormalities.
- CNV analysis of miscarriage tissue revealed embryonic mosaicism in both cases.
- The findings emphasize the importance of patient counseling and prenatal diagnosis despite PGT-A results.

## Abstract

Even after the transfer of euploid embryos selected by Preimplantation Genetic Testing for Aneuploidy (PGT-A), clinical pregnancies may still result in miscarriage. The subsequent detection of chromosomal copy number variations (CNVs) in the products of conception in some cases reflects the inherent limitations of PGT-A technology.

Two couples underwent PGT-A treatments at assisted reproduction center of Northwest Women's and Children's Hospital, with the respective indications of recurrent pregnancy loss and advanced maternal age. For both, ovarian stimulation was conducted by an antagonist protocol, followed by intracytoplasmic sperm injection (ICSI). The embryos were cultured to the blastocyst stage, at which timepoint trophectoderm biopsy was performed. Following genetic analysis, available euploid blastocysts were identified for both couples. However, both pregnancies were identified as missed abortions during the first trimester after transferring one euploid blastocyst each. Subsequent CNV analysis carried out on the products of conception showed the presence of embryonic mosaicism.

The two cases highlight the critical need for thorough patient counselling regarding the technical constraints as well as the potential risks of PGT-A. Additionally, they emphasize the indispensable value of prenatal diagnosis after transfer of euploid blastocyst identified by PGT-A.