In most of the systems used in embryo grading, Grade 4 is the lowest score. In other words, it is the score given to the embryos of the poorest quality. These are the embryos which have less of a chance of progressing on to implantation and pregnancy. They occur in the vast majority of In-Vitro Fertilizations (IVF), as there is generally a mixture of all the grades to be found. In the case of most couples, there are good quality, high-grade embryos to transfer.
Assessment of Grade 4 Embryos
The Grade 4 embryos are assessed on the basis of the same criteria as the other grades are. These are as following:
- Number of cells. Grade 4 embryos will lag behind in terms of the number of cells which are expected to be seen on any particular day in the development of the embryo. It will be slower in cleaving the cells. This is associated with a poorer outcome.
- The appearance of the cells – the Grade 4 cells are irregular in shape, size and surface texture. It is not easy for them to have cell-to-cell contact, with these vast differences.
- Fragmentation. So much of the cytoplasm can be fragmented, that it can become difficult to see the cells at all. This undoubtedly accounts for a lot of the irregularity of the cells, and results in much less effective cellular functioning.
- Nuclear content. Here we have our greatest cause for concern. Because of the disruption of the cellular content, the nuclei are seriously disturbed, and the DNA is disrupted. This can, and frequently does, result in genetic defects.
Chromosomal Abnormalities in Grade 4 Embryos
Whether it is due to the fragmentation or the disrupted nuclei, there is a higher rate of chromosomal abnormalities in Grade 4 embryos. Many of these embryos, if they do implant, spontaneously abort. There are those that don’t spontaneously abort, and which might go on to the birth of a child, which may then have a genetic defect. This may be present in a variety of ways – from neurological, to mental development, to outwardly visible physical differences.
This is not necessarily an inherited genetic abnormality. This abnormality may have occurred following the fertilization process. In IVF, one is not going to get a great many opportunities to try and conceive. So, with this in mind, and looking at the above issues, one can see the importance of being as selective as possible in choosing the embryos to transfer to the uterus in the hopes of implantation.