Table 5. Sjoblom Cecilia Classification System
Classification	Description
A	Expanded blastocyst (blastocele cavity over 50% of volume), larger than a cleaving stage embryo with a thinning zona pellucida. Must have a clear inner cell mass and cohesive trophectoderm.
B	Fully formed blastocyst with a clear inner cell mass and cohesive trophectoderm but not yet expanded with a non-thinning zona pellucida.
C	Blastocyst with small/no inner cell mass and/or irregular/interrupted trophectoderm and/or excluded/degenerate cells.
Cavitation	Evidence of a cavity of any size forming within the embryo, two distinct cell types not yet visible
Compacting	Evidence of any signs of compaction between cells of the embryo.
(Richardson et al., 2015).