Eggs, sperm & embryos
Only mature eggs, described as metaphase II, can be fertilised. Some collected eggs are immature or post-mature and cannot be used, which is why the number of eggs collected is usually higher than the number that can be injected or inseminated. Maturity is assessed by the embryologist on the day of collection.
Also known as: mature egg, MII, metaphase II, immature egg
Related South Africa guides
Sources
- ESHRE guidelines and patient information
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.