Blastocyst

Reaching the blastocyst stage indicates continued development and helps the laboratory choose between embryos. Not all fertilised eggs reach it, which is normal and is one reason cycles can yield fewer embryos than the number of eggs collected.

Also known as: day 5 embryo, blast

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.