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Updated: Aug 6, 2026
Chromosome Screening of Human Preimplantation Embryos by Using Spent Culture Medium: Sample Collection and Chromosomal Ploidy Analysis
Published on: September 7, 2021
Preimplantation Genetic Testing and Embryo Mosaicism: A Critical Narrative Review of Clinical Outcomes and
Daichi Inoue1, Yoshimasa Asada1
1Department of Reproductive Medicine, Asada Ladies Nagoya Clinic, Nagoya, Aichi, Japan.
Background And Aims:
Preimplantation genetic testing for aneuploidy (PGT-A) is widely used to select euploid embryos in patients at higher risk of transmitting genetic abnormalities during assisted reproductive technology (ART). Advances in PGT-A have resulted in the increased detection of embryo chromosomal mosaicism. This review aims to update clinicians and researchers on the implications of mosaicism in ART and emerging clinical outcomes from the use of mosaic embryo transfer cycles.
Methods:
A critical narrative review of the current literature was conducted, focusing on clinical outcomes of mosaic embryo transfers, the reliability of mosaicism detection in blastocyst trophectoderm biopsy, and controversies surrounding mosaicism thresholds and their clinical significance in ART. Literature was identified through searches of PubMed and relevant databases focusing on studies related to PGT-A and embryo mosaicism. As this is a narrative review, no statistical analysis was performed. We conducted a critical narrative review of articles published between January 2015 and May 2026 identified through searches of PubMed, Embase, and the Cochrane Library using terms related to PGT-A, mosaicism, and IVF outcomes, including original studies, society guidelines, and position statements.
Results:
Recent findings demonstrate that mosaicism detected in blastocyst trophectoderm does not always reflect the chromosomal constitution of subsequent embryonic-fetal development. Mosaic embryo transfers can result in healthy clinical outcomes, avoid embryo wastage, and potentially reduce the number of ART cycles. However, such transfers result in reduced implantation rates and higher miscarriage rates, notably with embryos exhibiting complex and high-level mosaicism. Genetic testing is more reliable with high-level mosaicism, and defining a high-level threshold presents one strategy to prioritize mosaic embryos for transfer.
Conclusion:
Future research should determine the clinical factors that may influence mosaicism and whether a threshold of mosaicism can improve clinical outcomes. Understanding the benefits versus potential risks of mosaicism will provide important information for patients, counselors, and clinicians in the selection and management of mosaic embryos in ART.
