Embryology
Eggs collected at egg pick-up are graded in the laboratory as mature (metaphase II), immature or post-mature. Only mature eggs can normally be fertilised, which is why the number collected is usually higher than the number fertilised. Maturity depends on stimulation, trigger timing and individual factors.
Also known as: metaphase II, MII egg, mature egg
Sources
- Royal Australian and New Zealand College of Obstetricians and Gynaecologists (ranzcog.edu.au)
- Australian and New Zealand Assisted Reproduction Database, National Perinatal Epidemiology and Statistics Unit, UNSW Sydney (npesu.unsw.edu.au)
Last reviewed: 10 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.