IVF Collapsed Expanded Blastocyst.
While the thin zona pellucida is still intact, the blastocele of the embryo on the bottom has collapsed (Code 1). The top two embryos are Code 4 because of the stage of development is retarded for their age (day 8). [Code 1: excellent or good; Code 2: fair; Code 3: poor; Code 4: dead or degenerating].
Hansen PJ (2006)