Embryology
The inner cell mass is the compact cluster of cells inside a blastocyst that develops into the fetus. Its appearance is graded A, B or C as part of blastocyst grading, alongside the trophectoderm and the degree of expansion.
Also known as: ICM
Sources
- European Society of Human Reproduction and Embryology (eshre.eu)
- Royal Australian and New Zealand College of Obstetricians and Gynaecologists (ranzcog.edu.au)
Last reviewed: 10 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.