Embryo Grading
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Most (but not all) clinics give embryos a grade based on how they look. The higher the grade, the better the quality of the embryo. However, an embryo's grade isn't necessarily predictive of how well that embryo will fare. Embryos with perfect grades can be abnormal, and the poorest graded embryo in a batch can be the only one to result it a baby. PGS testing is much more reliable in determining an embryo's chance for success.
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To make things even more complicated, not all clinics use the same grading system. Some will merely tell you that they look excellent, good, fair, or poor.
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Image source: Wikimedia Commons
Blastocyst Grading
Most clinics use the Gardener Grading System, or a variation of it. Therefore, that is the grading system that I will describe here.
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This system uses 3 characters to express each embryo's grade.
First is a number from 1-6, which indicates the embryo's expansion grade.
Second is a letter from A-C, which indicates the embryo's inner cell mass (ICM) grade.
Third is a letter from A-C, which indicates the embryo's trophectoderm (TE) grade.
With this grading system, the best grade is 6AA and the worst grade is 1CC.
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For more information about embryos, see the Embryo Stages & Ages page.
Expansion Grade
ICM Grade
1
2
3
4
5
6
-Blastocoel cavity less than half the volume of the embryo
-Blastocoel cavity more than half the volume of the embryo
-Full blastocyst, cavity completely filling the embryo
-Expanded blastocyst, cavity larger than the embryo, with thinning of the shell
-Hatching out of the shell
-Hatched out of the shell
A
B
C
-Many cells, tightly packed
-Several cells, loosely grouped
-Very few cells
TE Grade
A
B
C
-Many cells, forming a cohesive layer
-Few cells, forming a loose epithelium
-Very few large cells
3 Day Embryo Grading
Most clinics will give an update of your embryos' progress on day 3. These embryos are judged by how many cells they have, which should be between 6-10. On day 3, 8 cells is a quality embryo. 6 cell embryos are worth transferring, but they have a lower success rate. Also, at this stage there can be an odd number of cells.
Some clinics will also give a number to indicate quality. High quality embryos are symmetrical, have similar sized cells, and have little to no fragmentation.
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Check out this site for more information and pictures of day 3 embryos.
