There are several classifications of the quality of embryos that are on the first days of development. First of all, the specialist looks at the number of cells.
Normally, on the 2nd day of development, the embryo consists of 2-4 cells, on the 3rd day – from 6-8, and on the 4th day – the number of cells is difficult to count because their fusion begins and the embryo turns into a morula.
When describing an embryo 2-3 days of development, a letter indicating the quality and morphology of the blastomeres themselves and the presence or absence of fragmentation are added to the number indicating the number of blastomeres.
- nuclear-free fragments are absent, blastomeres are even, of the same size, have one nucleus, homogeneous cytoplasm
- the number of nuclear-free fragments of the cytoplasm reaches 25%, but does not exceed this limit;
- the number of fragments without nuclei ranges from 25 to 50%, there are irregularities in the size and shape of the blastomeres, there are inclusions in the cytoplasm;
- more than 50% of nuclear-free fragments, etc.