Hey, my name is Sean, but I also go by Embryoman, and I'm here today to talk to you about blastocyst or day 5 grading. First let's look at some key parts of the blastocyst. The zona is the shell that surrounds the embryo, the intercell mass or ICM goes on the form of fetus and the trafectoderm goes on the form of the placenta. When it comes to the actual embryo grade, the number refers to the expansion and goes from 1 to 6. The first letter refers to the quality of the ICM, which can be A, B or C, and The second letter refers to the quality of the trifectoderm.

As the expansion number increases, the embryo's size generally increases too. A blastocyst with an expansion of 3 is generally smaller than 1 with expansion 4. ICM and trifectoderm quality depend on the number of cells present. An A-grade ICM has more cells than a C-grade ICM, and an A-grade trifectoderm has more cells than a C-grade trifectoderm. Embryo grading is used to rank embryos for transfer, as embryos of higher quality tend to have a better chance than embryos of lower quality.

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