Cleavage Stage
The early embryonic development phase characterized by cell division without significant size increase.
Full Definition
The cleavage stage encompasses embryonic development from fertilization through day 3, during which the embryo undergoes rapid cell divisions (cleavages) without overall growth in size. Each division produces smaller cells called blastomeres. Normal progression includes 2-cell stage (day 1), 4-cell stage (day 2), and 6-8 cell stage (day 3). Embryo quality is assessed based on cell number, fragmentation, and uniformity. Cleavage stage embryos may be transferred on day 2 or 3, though extended culture to blastocyst stage is increasingly preferred for better selection.
Usage
Usage note: Distinguished from later developmental stages by the absence of cell differentiation.
In Context
- "The cleavage stage embryo showed normal development with 8 cells on day 3." — Embryology assessment
- "Transfer was performed at cleavage stage due to limited embryo availability." — Treatment summary