In this first article George Koustas, Director of Embryology at The Agora Clinic, explains embryo fragmentation and grading.
Day 2 and 3 embryo grading
The day after your eggs have been collected, the embryologists assess the growth of your embryos in the laboratory and provide you with updates. The embryologists do not assess your embryos daily as they prefer to disturb your embryos as little as possible from the culture incubators. One of the most important steps of your fertility journey is the embryo growth end embryo grading as this is how we can identify the embryo with the greatest implantation potential. Some patients often feel disheartened if some of their embryos are of “lower grade” following the laboratory assessment.
What is embryo grading?
Embryo development starts from the first cell and embryos continuously grow to 2, 4, 8- cells and so on. Embryo grading is based on morphological assessment ie how your embryos look 2 to 3 days after your egg collection.
Two days after your egg collection the embryos should have 2 to 4 cells, at 3 days they should have 6 to 8 cells and at 5 days they should be at the blastocyst stage. During these different stages of development, the embryos should have a certain number of cells and appearance. Each embryo will be assessed for the number of cells, percentage of fragmentation and how is the shape of the cells ie even or not even based on a national standardised scheme.
Fragmentation volume and cell regularity are expressed in a scale from 1 to 4, with 4 being the highest grade and 1 the lowest. For example, an 8-cell 4/4 grade is a day 3 top quality 8-cell embryo with even cells and no fragmentation. A 4-cell 2/2 grade is an average quality 4-cell embryo with uneven cells and moderate fragmentation.
What is embryo fragmentation?
Embryo fragmentations are tiny structures in the embryo, detached from the cells. They look like little cells, but they are not cells. Many reasons cause embryo fragmentation and it is a natural phenomenon. A high degree of fragmentation is linked with lower success rates.
On the other hand image below, we have seen for years that embryos with fragmentation on day 2 or day 3 of embryo development can lead to successful pregnancies and live births. The left-hand side photo shows an embryo with mild fragmentation and the right-hand side an embryo with none. Both resulted in healthy live births, so don’t feel disheartened if your embryos display fragmentation and are of “lower grade”. It is normal to have embryos with a mixture of grades.