Embryology
About 16 to 18 hours after insemination or ICSI, a normally fertilised egg shows two pronuclei — one from the egg and one from the sperm. Eggs with one or three pronuclei have fertilised abnormally and are not used for transfer. This check is the basis of the fertilisation report you receive on day one.
Also known as: 2PN, pronuclei, normal fertilisation
Related Australia guides
Sources
- European Society of Human Reproduction and Embryology (eshre.eu)
- Royal Australian and New Zealand College of Obstetricians and Gynaecologists (ranzcog.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.