Glossary · Definition · v2026.3
What Is the Inner Cell Mass (ICM)?
The inner cell mass is a cluster of cells inside a blastocyst-stage embryo that will eventually develop into the fetus. It is distinct from the surrounding trophectoderm cells.
Clinical significance
The structure and appearance of the inner cell mass are considered during embryo grading and can influence decisions about which embryos are selected for transfer or cryopreservation.
Common confusion
Some assume the inner cell mass alone determines embryo viability, but successful development depends on both the inner cell mass and the trophectoderm as well as other biological factors.
Related reference
Used in
This content defines terminology for educational orientation. It does not constitute medical advice.
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