cleavage stage embryo
Early embryo developmental stage from day 1-3 post-fertilization characterized by cell division without growth.
Full Definition
A cleavage stage embryo refers to the developmental period from fertilization through approximately day 3, during which the embryo undergoes rapid cell divisions without significant increase in overall size. During this stage, the embryo progresses from a single-cell zygote through 2-cell, 4-cell, and typically 6-8 cell stages by day 3. Cleavage stage embryos are surrounded by the zona pellucida and have not yet formed a blastocoel cavity. In IVF practice, embryo quality assessment at the cleavage stage considers cell number, symmetry, fragmentation percentage, and presence of multinucleation. Many IVF programs now culture embryos to blastocyst stage rather than transferring at the cleavage stage.
Usage
Usage note: Often contrasted with blastocyst stage in transfer timing decisions
In Context
- "Two grade A cleavage stage embryos were selected for transfer on day 3." — Embryology report
- "Extended culture to blastocyst was preferred over cleavage stage transfer." — Laboratory protocol