Eggs, sperm & embryos
As cells compact, individual boundaries become hard to see, forming a morula. It is a normal step between the cleavage stage and the blastocyst.
Also known as: day 4 embryo, compaction
Related Canada guides
Sources
- Canadian Fertility and Andrology Society (CFAS)
Last reviewed: September 9, 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.