Blastulation

Blastulation is the development from a compacted morula into a blastocyst with a fluid-filled cavity, usually on day 5. Some embryos blastulate a day later, on day 6, and can still be frozen and transferred successfully. Embryos that never blastulate are not suitable for transfer.

Also known as: blastocyst formation

Last reviewed: 8 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.