Firstly, we grade embryos according to the development phase. Morula (M), Early Blastocyst (EB), Blastocyst (B), Expanded Blastocyst (XB) and Hatched (H) are the common developmental phase with embryo transfer.
Thereafter we grade according to quality. Grade 1, 2, 3, degenerate or oocyte.
- Grade 1 Embryos: where more than 85% of the total cellular material of the embryo is alive and normal
- Grade 2 Embryos: between 50% and 85% of the total cellular material is alive and normal
- Grade 3 Embryos: where less than 50% of the total cellular material is alive and normal
- Degenerates are unviable embryos (dead) and Oocytes are unfertilized gametes.
Grade 1 embryos are most likely to survive, with conception rates up to 60% with embryo transfer. Whereas grade 2 and 3 embryos have a conception rate as low as 30%.
Grade 1 embryos are also preferred with cryopreservation (freezing). The conception of frozen-thawed embryos decrease with 10% of their fresh ability.
Example of embryo grading: We will write M1 on the embryo flush sheet, which means Morula + Grade 1.