Embryonic Mosaicism in Clinical Practice: Interpretation of PGT-A Results and Patient Management Strategies (review)

Elective single embryo transfer (eSET) is a cornerstone of modern reproductive medicine, aimed at achieving a healthy singleton birth while minimizing the risks associated with multiple pregnancies. Enhancing its efficacy requires the refinement of embryo selection methods, among which preimplantation genetic testing for aneuploidy (PGT-A) holds significant importance. The widespread adoption of PGT-A, particularly through next-generation sequencing (NGS), has led to an increased detection of mosaic embryos, which contain a mixture of euploid and aneuploid cells.
This literature review examines the biological underpinnings of embryo mosaicism, whose primary cause is mitotic errors during early embryogenesis. The challenges of laboratory diagnosis and the interpretation of PGT-A results are analyzed in detail, focusing on technical limitations, variability in diagnostic thresholds, and the discordance in chromosomal status between the trophectoderm and the inner cell mass.
Data from clinical studies on the outcomes of mosaic embryo transfers are presented. The evidence indicates that pregnancy and live birth rates following the transfer of embryos with low– and intermediate-level mosaicism can be comparable to those achieved with euploid embryos.
The positions of international professional societies (ESHRE, ASRM, PGDIS) are reviewed. These bodies concur that mosaic embryos should not be considered a priori unsuitable for transfer. The decision to transfer such embryos must be deliberate, involving a genetic counselor or clinical geneticist, and tailored to the individual patient’s circumstances. While the transfer of euploid embryos remains the priority, mosaic embryos represent a viable alternative when no euploid embryos are available, with prenatal diagnostic testing being strongly recommended in these cases.

1. Geng T., Zhou Q., Wang Y. et al. Comparison of pregnancy outcomes for high morphological scoring mosaic vs. low morphological scoring euploid embryos: a retrospective cohort study. J Ovarian Res. 2025;18(1):79.

2. Vanneste E., Voet T., Le Caignec C. et al. Chromosome instability is common in human cleavage-stage embryos. Nat Med. 2009;15(5):577-583.

3. Babariya D., Fragouli E., Alfarawati S. et al. The incidence and origin of segmental aneuploidy in human oocytes and preimplantation embryos. Hum Reprod. 2017;32(12):2549-2560.

4. Munné S., Wells D.. Detection of mosaicism at blastocyst stage with the use of high-resolution next-generation sequencing. Fertil Steril. 2017;107(5):1085-1091.

5. Popovic M., Dheedene A., Christodoulou C. et al. Chromosomal mosaicism in human blastocysts: the ultimate challenge of preimplantation genetic testing? Hum Reprod. 2018;33(7):1342-1354.

6. Chavli E., van den Born M., Eleveld C. et al. Chromosomal mosaicism in human blastocysts: a cytogenetic comparison of trophectoderm and inner cell mass after next-generation sequencing. Reprod Biomed Online. 2022;45(5):867-877.

7. De Rycke M., Capalbo A., Coonen E. et al. ESHRE survey results and good practice recommendations on managing chromosomal mosaicism. Hum Reprod Open. 2022;2022(4):hoac044.

8. Palmerola K.L., Vitez S.F., Amrane S. et al. Minimizing mosaicism: assessing the impact of fertilization method on rate of mosaicism after next-generation sequencing (NGS) preimplantation genetic testing for aneuploidy (PGT-A). J Assist Reprod Genet. 2019;36(1):153-157.

9. Wang Y., Li R., Yang R. et al. Intracytoplasmic sperm injection versus conventional in-vitro fertilisation for couples with infertility with non-severe male factor: a multicentre, open-label, randomized controlled trial. Lancet. 2024;403(10430):924-934.

10. Greco E., Minasi M.G., Fiorentino F. Healthy Babies after Intrauterine Transfer of Mosaic Aneuploid Blastocysts. N Engl J Med. 2015;373(21):2089-2090.

11. Capalbo A., Poli M., Rienzi L. et al. Mosaic human preimplantation embryos and their developmental potential in a prospective, nonselection clinical trial. Am J Hum Genet. 2021;108(12):2238-2247.

12. Tise C.G., Verma K., Rivera-Cruz G. et al. Healthy euploid dizygotic twin birth after transfer of nonmosaic aneuploid embryos. Fertil Steril. 2025.

13. The Practice Committee of the American Society for Reproductive Medicine. Clinical management of mosaic results from preimplantation genetic testing for aneuploidy of blastocysts: a committee opinion. Fertil Steril. 2023;120(5):973-982.

14. Leigh D., Cram D.S., Rechitsky S. et al. PGDIS position statement on the transfer of mosaic embryos 2021. Reprod Biomed Online. 2022;45(1):19-25.