Embryology
A blastocyst has a fluid-filled cavity, inner cell mass and trophectoderm. It's the stage most embryos are transferred at.
Also known as: blast, day 5 embryo, day 6 embryo
Related United Kingdom guides
Last reviewed: 23 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.