Mosaic embryo

A mosaic embryo has a mixture of chromosomally normal (euploid) and abnormal (aneuploid) cells within the same biopsy sample, rather than a uniformly normal or abnormal result. Mosaicism is reported as low-level (a smaller proportion of abnormal cells) or high-level (a larger proportion), and it can also be segmental, affecting only part of a chromosome rather than a whole one. Mosaic results are more complex to interpret than clear euploid or aneuploid results, and clinics vary in how they classify and counsel about them. Some mosaic embryos, particularly low-level mosaics, have gone on to healthy pregnancies when transferred after genetic counselling, but data are still developing and outcomes are not guaranteed. Decisions about whether to transfer, and in what order relative to euploid embryos, should always involve genetic counselling and full discussion of the uncertainties with the treating team.

Also known as: mosaicism, low-level mosaic, high-level mosaic, segmental mosaicism

Last reviewed: 9 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.