Understanding IVF Embryo Grading

Written By Rena Gower

One of the biggest stressors my patients face is waiting for embryo grading results.  It usually takes two weeks to get results on developing embryos and this time period is often fraught with nerves and anxious clicking of the “refresh” button in the patient portal to see if anything comes in.  When the results do come in, the googling usually starts to try and understand what the grades mean. 

All of my patients know how much I loathe “Dr. Google” and I recorded this episode with Christine Briton-Jones, a clinical embryologist and Director of Laboratory Services at Reproductive Medicine Associates of New York (RMA of New York) to have a reliable resource to turn to to answer all questions relating to embryo grading. 

What is Embryo Grading?

Embryo grading is a way for doctors to assess the quality of embryos created during IVF. Embryo grading is a tool that helps determine which embryos are the best candidates for transfer. Grading provides an explanation as to why some embryos are better for transfer than others may be. 

Day 3 Grading

On Day 3 after fertilization, embryos are still dividing into cells. The grading looks at:

  • The number of cells (ideally between 6-10)

  • Symmetry of the cells – comparing size and shape

  • The amount of fragmentation (pieces that may have broken off)

    • Ex: high cell, low fragmentation is ideal

Grades are usually given as letters (A, B, C) or numbers (1, 2, 3), with A or 1 being the highest quality. 

Day 5 Grading

By Day 5, embryos have developed into a blastocyst stage. Grading at this point is a bit more detailed and considers:

  1. How expanded the embryo is

  2. The quality of the inner cell mass (ICM), which is responsible for making the baby 

  3. The quality of the embryo’s outer layer (trophectoderm)

A common grading system uses a combination like 5AA:

  • The number shows how expanded the embryo is (1-6)

  • The first letter grades the ICM (A, B, or C):

    • A: many cells that are tightly packed

    • B: some cells loosely assembled

    • C: few cells 

  • The second letter grades the trophectoderm – creates the placenta 

Why Embryo Grading Can Be Subjective

Christine explains on the podcast that embryo grading isn't always straightforward and requires experience to interpret correctly. Here are some key points to remember:

  1. Grading isn't everything (I can’t emphasize this enough!): While higher grades usually mean better chances for pregnancy, lower-graded embryos can still lead to successful pregnancies.

  2. Embryos can improve: An embryo's grade can change as the embryo develops. For example, a C-grade embryo might become an A-grade embryo by the next day.

  3. It's one part of the picture: Grading is just one factor in deciding which embryos to use, along with other patient-specific details, such as age and medical history.

Finding Hope in Embryo Grading

Christine also offers some encouraging thoughts:

  1. Celebrate all grades: Even C-grade embryos can result in healthy pregnancies.

  2. Grading is a snapshot: It reflects a moment in time, rather than an embryo's full potential for growth.

  3. Embryos continue to develop: They can get better over time after grading occurs.

Conclusion

As we say on the podcast, knowledge is power and understanding embryo grading can help you feel more informed during your IVF journey. If you just got your embryo results back and you’re feeling disappointed, please remember one of the biggest takeaways from this episode– embryo grading isn’t everything! It’s a snapshot of embryo quality, but embryo quality can continue to improve. A C-grade embryo has the potential to develop into an A grade embryo. Please remember that while grading provides useful information, it’s not the only factor in making decisions about embryo transfer.  This is just one measure of data to have as you move through on your journey. One of the most important things to remember is that you have this data and that in itself is a win–take some time to celebrate the accomplishment of putting in the work to collect this information.  This is a huge step forward and should be acknowledged as such. 


Listen to the full podcast below!

Rena Gower