Mosaic Embryo
An embryo containing both chromosomally normal and abnormal cells, presenting intermediate genetic test results.
Full Definition
A mosaic embryo is one that contains a mixture of chromosomally normal (euploid) and abnormal (aneuploid) cells following preimplantation genetic testing. Mosaicism can arise from post-zygotic chromosomal errors during early embryonic development and is detected when genetic testing shows intermediate results between normal and abnormal thresholds. The clinical significance of mosaicism depends on the percentage of abnormal cells and the specific chromosomes involved. While mosaic embryos have lower implantation and live birth rates compared to euploid embryos, they may still result in healthy pregnancies, making their management controversial and requiring careful counseling.
Usage
Usage note: Requires careful explanation to patients regarding uncertain prognosis and need for genetic counseling.
In Context
- "The mosaic embryo showed 30% aneuploid cells and required extensive counseling before transfer." — Genetic counseling session
- "Current guidelines suggest mosaic embryos may be considered for transfer when euploid embryos are unavailable." — Clinical practice guideline