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I wasn't expecting to hear from embryology today, but imagine my surprise when I got a call from the embryologist this afternoon with the day 5 report. Before I tell you how many embryos made it to the blast stage, let me explain the blastocyst grading (from what I understand). There are three components that go into the grading of the embryo: (1) blastocyst development status, (2) inner cell mass score, and (3) trophectoderm score.
The blast development status (expansion - hatching stage) is indicated by the number in the front. The number ranges from 1 to 6, with 1 being the lowest and 6 being the highest quality.
1 = Blastocoel cavity less than half the volume of the embryo.
2 = Blastocoel cavity greater than than half the volume of the embryo.
3 = Full blast, cavity completely filling the embryo.
4 = Expanded blast, cavity larger than the embryo with thinning of the shell.
5 = Hatching out of the shell.
6 = Hatched out of the shell.
The first letter is the grade of the inner cell mass (the cells that will become the fetus). The letters range from A to C, with A being the highest and C being the lowest quality.
A = Many cells, tightly packed.
B = Several cells, loosely grouped.
C = Very few cells.
The second letter is the grade of the trophectoderm (future placenta cells). Again, the letters range from A to C, highest to lowest quality.
A = Many cells, forming a cohesive layer.
B = Few cells, forming a loose epithelium.
C = Very few large cells.
Today, out of the 22 embryos, there were 10 embryos that have grown to the blastocyst stage, quality ranging from 2/3 to 3BB to 3AB to 3AA to 5AA. The 2/3 grade is the earliest blast stage, almost a grade 3 but not quite. She said that she went ahead and biopsied them because if they wait until tomorrow, the embryo might already be hatched. And doing a biopsy on hatched embryos isn't preferred. I wished that I had asked her how many blasts at each grade, but I was just so excited to get the day 5 report. Anyway...The embryologist biopsied the 10 blasts and then vitrified them about an hour later.
Tomorrow, she will check on the 12 remaining embryos, and hopefully they all will be good enough for biopsy. But then again, she did tell me that roughly 40 - 50% of the embryos only make it to blast. So I'm anxiously waiting for tomorrow's call.