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Blastocysts are Day 5 Embryos, wherein they have more than 100 Cells in them.
A blastocyst is the final stage of the embryo's development before it hatches out of its shell (zona pellucida) and implants in the uterine wall.
BLASTOCYST GRADING
This blastocyst grading system assigns 3 separate quality scores to each blastocyst embryo:
- Blastocyst development stage - expansion and hatching status
- Inner cell mass (ICM) score, or quality
- Trophectoderm (TE) score, or quality
- Blastocysts are given a quality grade for each of the 3 components and the score is expressed with the expansion grade listed first, the inner cell mass grade listed second and the trophectoderm grade third. For example, a blastocyst quality grade of 4AB means that the blastocyst is expanded (grade 4), has many tightly packed cells in the inner cell mass (grade A), and has a trophectoderm with few cells forming a loose epithelium (grade B). See the examples of blastocyst grading pictures below.
grade
grade
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EARLY BLASTOCYSTS
Early Blastocysts with Very little Cavity (Blastocele) (Cant Grade them)
(I) Inner Cell mass : Can’t Grade
(T) Trophectoderm : Can’t Grade
EARLY BLASTOCYSTS
Blastocysts with Cavity (Blastocele) less than ½ Volume of Embryo (Grade1)

1AA

1AB
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)
(I) Inner Cell mass = Grade A (very Good)
(T) Trophectoderm = Grade B (Poor)

1BB

1CC
(I) Inner Cell mass = Grade B (Poor)
(T) Trophectoderm = Grade B (Poor)
(I) Inner Cell mass = Grade C (Very Poor)
(T) Trophectoderm = Grade C (Very Poor)
INTERMEDIATE STAGE BLASTOCYST
Cavity (Blastocele) will be More than ½ the Volume of Embryo (Grade 2)

2AA

2AB
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)
(I) Inner Cell mass = Grade A (very Good)
(T) Trophectoderm = Grade B (Poor)

2BB

2CC
(I) Inner Cell mass = Grade B (Poor)
(T) Trophectoderm = Grade B (Poor)
(I) Inner Cell mass = Grade C (Very Poor)
(T) Trophectoderm = Grade C (Very Poor)
INTERMEDIATE STAGE BLASTOCYST
Cavity (Blastocele) will completely fill the Volume of Embryo (Grade 3)

3AA

3AB
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)
(I) Inner Cell mass = Grade A (very Good)
(T) Trophectoderm = Grade B (Poor)

3BB

3CC
(I) Inner Cell mass = Grade B (Poor)
(T) Trophectoderm = Grade B (Poor)
(I) Inner Cell mass = Grade C (Very Poor)
(T) Trophectoderm = Grade C (Very Poor)
Fully Expanded Blastocyst (Grade 4)
Large, well expanded

4AA

4AB
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)
(I) Inner Cell mass = Grade A (very Good)
(T) Trophectoderm = Grade B (Poor)

4BB

4CC
(I) Inner Cell mass = Grade B (Poor)
(T) Trophectoderm = Grade B (Poor)
(I) Inner Cell mass = Grade C (Very Poor)
(T) Trophectoderm = Grade C (Very Poor)
HATCHING BLASTOCYST (GRADE 5)
BLASTOCYST HATCHING OUT OF ZONA
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)
COMPLETELY HATCHED BLASTOCYST (GRADE 6)
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)