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.

Expansion
grade

Blastocyst development and stage status

1

Blastocoel cavity less than half the volume of the embryo

2

stocoel cavity more than half the volume of the embryo

3

Full blastocyst, cavity completely filling the embryo

4

Expanded blastocyst, cavity larger than the embryo, with thinning of the shell

5

Hatching out of the shell (Zona)

6

Hatched out of the shell (Zona)

ICM
grade

Inner cell mass quality

A

Many cells, tightly packed

B

Several cells, loosely grouped

C

Very few cells

TE
grade

Trophectoderm quality

A

Many cells, forming a cohesive layer

B

Few cells, forming a loose epithelium

C

Very few large cells

EARLY BLASTOCYSTS

Early Blastocysts with Very little Cavity (Blastocele) (Cant Grade them)

Early Blastocyst

Early Blastocyst

(C) Cavity is Very Small
(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)

Top Quality

1AA

Good

1AB

(C) Cavity < ½ Embryo’s Volume Volume = Grade 1
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)

(C) Cavity < ½ Embryo’s Volume = Grade 1
(I) Inner Cell mass = Grade A (very Good)
(T) Trophectoderm = Grade B (Poor)

Poor

1BB

Very Poor

1CC

(C) Cavity < ½ Embryo’s Volume = Grade 1
(I) Inner Cell mass = Grade B (Poor)
(T) Trophectoderm = Grade B (Poor)

(C) Cavity < ½ Embryo’s Volume = Grade 1
(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)

Top Quality

2AA

Good

2AB

(C) Cavity > ½ Embryo’s Volume = Grade 2
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)

(C) Cavity > ½ Embryo’s Volume = Grade 2
(I) Inner Cell mass = Grade A (very Good)
(T) Trophectoderm = Grade B (Poor)

Poor

2BB

Very Poor

2CC

(C) Cavity > ½ Embryo’s Volume = Grade 2
(I) Inner Cell mass = Grade B (Poor)
(T) Trophectoderm = Grade B (Poor)

(C) Cavity > ½ Embryo’s Volume = Grade 2
(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)

Top Quality

3AA

Good

3AB

(C) Cavity Completely Fills Embryo = Grade 3
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)

(C) Cavity Completely Fills Embryo = Grade 3
(I) Inner Cell mass = Grade A (very Good)
(T) Trophectoderm = Grade B (Poor)

Poor

3BB

Very Poor

3CC

(C) Cavity Completely Fills Embryo = Grade 3
(I) Inner Cell mass = Grade B (Poor)
(T) Trophectoderm = Grade B (Poor)

(C) Cavity Completely Fills Embryo = Grade 3
(I) Inner Cell mass = Grade C (Very Poor)
(T) Trophectoderm = Grade C (Very Poor)

Fully Expanded Blastocyst (Grade 4)

Large, well expanded

Top Quality

4AA

Good

4AB

(C) Completely Expanded = Grade 4
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)

(C) Completely Expanded = Grade 4
(I) Inner Cell mass = Grade A (very Good)
(T) Trophectoderm = Grade B (Poor)

Poor

4BB

Very Poor

4CC

(C) Completely Expanded = Grade 4
(I) Inner Cell mass = Grade B (Poor)
(T) Trophectoderm = Grade B (Poor)

(C) Completely Expanded = Grade 4
(I) Inner Cell mass = Grade C (Very Poor)
(T) Trophectoderm = Grade C (Very Poor)

HATCHING BLASTOCYST (GRADE 5)

BLASTOCYST HATCHING OUT OF ZONA

Early Blastocyst

Early Blastocyst

Blastocyst Hatching out of Zona (shell) = Grade 5
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)

COMPLETELY HATCHED BLASTOCYST (GRADE 6)

Early Blastocyst

Blastocyst completely hatched = Grade 6
(I) Inner Cell mass = Grade A (Very Good)
(T) Trophectoderm = Grade A (Very Good)