Answer from: Andrea Sánchez Freire
A morphologically “perfect” blastocyst would be a AA; excellent inner cell mass and trophectoderm. When a blastocyst scores 5AA, the blastocyst is beginning to “hatch”. The number of the score indicates degradation of expansion of the embryo and the letters the score of the inner cell mass and trophectoderm. 5AA it would be a top grade embryo on day 5 or day 6. But it doesn’t mean that it’s an embryo in perfect condition, it would be morphologically top quality but we don’t know if it has any chromosomal abnormality.
Answer from: Michael Carroll, BSc, PhD, PgCAP, CBiol, FRSB, FIBMS, FHEA, FLS, ANSHCS
So what is considered a good embryo equality? Well, good embryo quality depends on the stage of development that embryo’s has been assessed at so, you could look at it, at the first day of the fertilization – that’s the kind of pronuclear stage. If they have two pronuclei (these little dots within the center of the cells) and everything looks good in terms of the structure, overall shape of the cell, that’s good. As the eggs divide or the embryos divide you’ll have a two cell, four cell, eight cell embryo. A good quality embryo will have symmetry, those two cells will look the same same size, same shape and as those cells divide into a four and eight cell stage embryo, it’s the same thing if those eggs, those embryos that have good symmetry and good shape tend to be good quality. The other thing is to look at the any granulations or fragmentations within the embryos itself like little small fragments of cells – if there’s lots of those, that can indicate poor quality and so you’ll be looking for fewer granulations and fewer fragmentations within the embryo grading system as well and as the embryo develops further, it goes through a stage called compaction and then it forms a blastocyst. The blastocyst is an embryo that am is usually at a stage where it implants into the uterus normally but they’re also assessed and a good quality blastocyst will be like a hollow bowl with a good structure around it the outer side as it did trophectoderm and then the inner cell mass (little tight selection of ball of cells within inner cells). There’s a grading system that is used in the UK and other countries. It depends if they follow national or international guidelines in terms of their grading system but each clinic will be able to monitor the development and quality of oocytes and greater quality of oocytes according to the grading system.
What is the average embryo grade?
Is a 4AA embryo good?