When embryo grading for In-Vitro Fertilization (IVF), one can find grade 3 amongst all of the other three grades. A couple might find themselves with a mixture, or mainly a specific one grade or another.
The embryos that develop after fertilization of the egg cell by the sperm are closely watched by the attending specialists. Obviously, the aim is to produce a successful pregnancy, leading to the birth of a healthy baby. The higher grade embryos are considered to be of better quality, and they are associated with a higher success rate (as measured in terms of the women becoming pregnant).
The embryos are graded according to specific aspects of their appearance:
The Number of Cells on a Particular Day
As the embryos develop, they start as a single cell – a zygote. This is the fertilized egg. It divides to form a 2-cell embryo, which divides to form a 4-cell embryo and so on. Some embryos are slower at the dividing (cleaving) than others, which means that on Day 3, when a Grade 1 embryo would have 8 cells, the Grade 3 embryo may only have 6 cells. This tends to be related to their eventual success rate.
Appearance of the Cells
In Grade 3, the cells are rather irregular in terms of size and shape, and the surfaces are less smooth. This affects their ability to have cell-to-cell contact, which they need as part of the ongoing development of the embryo.
Fragmentation
The cytoplasm, which is part of the inner content of the cells, can be seen in fragmented pieces around the cells. This is obviously worse than in Grade 2, which makes it (depending on the grading system) more than 10% or more than 25%. Whichever it may be, the result is less cytoplasm in the cells and more irregular cells.
Nuclear Content
This is more disturbed and less well organized as we go down the grading. The greatest concern here is that with the very disturbed nuclei, there is distortion of DNA, genes are affected, and potential for long-term problems is a reality. (This having occurred post-fertilization.)
If these embryos are used as part of an embryo transfer to the uterus, it would part of a multiple-embryo transfer. The chances of a single embryo transfer with a Grade 3 embryo being successful are minimal. These might be amongst the embryos that are chosen to be frozen. But, the success rate after thawing is lower than with fresh embryos, so their chances are lower than ever.
