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One of the ways to determine if an IVF pregnancy will be a success is by rating blastocysts and/or embryos before implantation.
One of the ways to determine if an IVF pregnancy will be a success is by rating blastocysts and/or embryos before implantation. A blastocyst is an embryo that has developed to the point of having 2 different cell components and a fluid cavity in the middle. While this is a very superficial way to rate the quality and viability or a pregnancy, reproductive specialists do use a rating system for blastocysts to provide the best guess for a successful embryo. The blastocyst rating system is a number followed by two letters (for example, “3BB”), and is based on a visual examination and rating of the blastocyst.
Rating Blastocysts follows a three-part system of grading. At Oregon Reproductive Medicine, we use the following chart for grading blastocyst success:
NUMBER: The degree of the expansion of the embryo’s cavity, ranging from 2-6
2 = cavity fills 1/3 of the embryo
3 = partial expansion, fills 70% of the embryo
4 = fully expanded cavity
5 = embryo has expanded and split open the zona
6 = embryo has completely hatched from the zona
FIRST LETTER: The inner cell mass (ICM) quality.
A = well defined clump of cells
B = less well defined; may be grainy in appearance
C = a few dark cells, appear degenerative
SECOND LETTER: The trophectoderm quality. The trophectoderm is the cell layer that makes the placenta and the membranes surrounding the baby.
A = many smooth cells, equal size, forming a neat layer
B = irregular cell layer, some grainy cells
C = very irregular cell layer, cells may be dark and/or grainy