Eggs, sperm & embryos
Attrition describes the natural narrowing at each stage: not every follicle holds an egg, not every egg is mature, not every mature egg fertilises, and not every fertilised egg becomes a usable blastocyst. Understanding this in advance makes each stage less alarming and explains why a good number of follicles does not guarantee several embryos.
Also known as: embryo attrition, the funnel, drop off
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.