Glossary · Definition · v2026.3
What Is Embryo Mosaicism Grading?
Embryo mosaicism grading is the classification of mosaic embryos based on the percentage of aneuploid cells detected in a trophectoderm biopsy, typically categorized as low-level (under 40%), moderate (40 to 80%), or high-level (over 80%) mosaicism.
Clinical significance
Low-level mosaic embryos may be considered for transfer when no euploid embryos are available, as some studies show they can result in healthy pregnancies. High-level mosaic embryos carry a significantly lower implantation rate and higher miscarriage risk. The specific chromosome involved also affects clinical decisions.
Common confusion
Mosaicism grading reflects the proportion of abnormal cells in the biopsy sample, not necessarily the entire embryo. Biopsy results may not perfectly represent the chromosomal makeup of the inner cell mass that forms the fetus.
Related reference
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This content defines terminology for educational orientation. It does not constitute medical advice.
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