Embryology
The morula is the stage between a cleavage-stage embryo and a blastocyst, where cells compact tightly together. It is rarely reported to patients because clinics usually assess on day three and day five, but it may be mentioned if development is running slightly behind.
Also known as: day 4 embryo, compaction
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.