A mosaic embryo is a term used to refer to an embryo that carries both chromosomally normal (euploid) and abnormal (aneuploid) cells as identified during preimplantation genetic testing for aneuploidy (PGT-A) as part of an in vitro fertilization (IVF) process.

Because a mosaic embryo contains a portion of abnormal cells, there is a risk of miscarriage or abnormal birth. Therefore, some fertility experts do not favor transferring mosaic embryos.