Embryo Grading Explained: What 4AA Really Means
Your embryology report is full of codes like 4AA, 3BB, and Day 5. Here is your definitive guide to decoding them.
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The Gardner Grading System (Day 5 Blastocysts)
Most clinics use the Gardner scale, which consists of a number and two letters (e.g., 4AA).
1. The Number (Expansion)
Describes how expanded the blastocyst is (1-6).
- 1-2: Early blastocyst (cavity is forming).
- 3: Full blastocyst (cavity fills the embryo).
- 4: Expanded blastocyst (cavity is larger than the original egg).
- 5: Hatching (cells are starting to break out of the shell).
- 6: Hatched (embryo has completely left the shell).
2. The First Letter (Inner Cell Mass)
Grades the cells that will become the baby.
- A: Many cells, tightly packed.
- B: Several cells, loosely grouped.
- C: Very few cells.
3. The Second Letter (Trophectoderm)
Grades the cells that will become the placenta.
- A: Many cells forming a cohesive layer.
- B: Few cells forming a loose layer.
- C: Very few large cells.
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Store your grading reports and PGT-A results securely in the TrackMyIVF app.
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Common Questions
Is a 'C' grade embryo bad?
Not necessarily. While 'A' and 'B' grades indicate higher cell count and symmetry, many healthy babies have been born from 'C' grade embryos. PGT-A testing is a better indicator of genetic health than visual grading.
What is the difference between Day 3 and Day 5?
Day 3 embryos (Cleavage Stage) have 6-10 cells. Day 5 embryos (Blastocysts) have 100+ cells and are much stronger. Most modern clinics prefer transferring Day 5 blastocysts.
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