Embryo grading: what do the scores mean

Embryo grading: what do the scores mean?

Embryo grading is a way for embryologists to assess the quality of embryos.

Embryo grading is done by examining the embryos under the microscope.

By determining embryo grades, the embryologist determines which embryos are better for higher rates of implantation and IVF success rate.

1. Day 3 grading:

• Cleavage stage
• Embryos are evaluated on day 2-3 after fertilization
• The embryologist evaluates: number of cells, cell symmetry and fragmentation
• On day 3 the number of cells should be 6-8
• Even cells are better
• Less fragmentation is better
• Grades are as follows:

** grade A: excellent embryos with even cells and minimal fragmentation

** grade B: slight unevenness, slight fragmentation. These embryos are good

**grade C: fair embryos with more fragmentation

** grade D: poor quality

2. Days 5 grading:

• Blastocyst stage
• We look at expansion, the more expanded the better
• We look at inner cell mas which becomes the baby, the more tightly packed cells the better
• We look at cells that become the placenta, many healthy cells mean better outcomes

We have to understand that better grading doesn’t guarantee success.

Lower-grade embryos can result in pregnancy.

Why do doctors prefer day 5 transfer?

• The selection of embryos is better
• Implantation rate is high
• The grading system is more accurate

Does embryologists experience affect embryo grading?

Yes, embryo grading is subjective and two embryologists might grade the same embryo differently.

What is the role of time-lapse imaging?

• These are new incubators which track embryo development
• They assess two things: division timing and patterns
• They help in embryo selection and decrease interpersonal differences

Dr Najeeb Layyous  F.R.C.O.G

Consultant Obstetrician, Gynecologist and Infertility Specialist