If you’re going through IVF, you’ve probably heard your medical team mention “embryo grading.” But what does this grading really mean, and how does it impact your success in IVF? Today, embryologist Alease Barnes takes us behind the scenes to understand how embryos are graded in the lab and why these details matter for your journey.

What Is Embryo Grading?

During an IVF cycle, the lab team will combine eggs and sperm and let them grow in culture for about five to seven days. By days five, six, or seven, these fertilized eggs reach what’s called the “blastocyst stage.” This is when Alease and her team grade the embryos, identifying the best-quality ones for transfer.

The Three Key Parts of Embryo Grading

When grading embryos, embryologists look at three main features:

  1. Expansion: This refers to the size of the embryo. Larger embryos are closer to hatching, which is an important step for implantation.
  2. Inner Cell Mass (ICM): The ICM is the clump of cells that will eventually form the baby. If you’ve ever seen an embryo under a microscope, it’s the tight bundle of cells on one side of the embryo. ICM is graded on a scale of A to D, similar to school grades—A is ideal, and D is the lowest grade. For high-quality ICM, embryologists look for compact cells with minimal cell death.
  3. Trophectoderm: Surrounding the ICM is the trophectoderm, the layer of cells that will develop into the placenta. A healthy trophectoderm should have a “cobblestone” appearance—lots of plump cells with no gaps. Like the ICM, the trophectoderm is graded from A (best) to D (least ideal).

Understanding Embryo Grades: What Do “4AB” and “3BC” Mean?

Embryos are assigned a grade combining numbers and letters, such as “4AB” or “3BC.”

Embryo Grading 101: The Gardner Scale

The number reflects the embryo’s stage of expansion, while the first letter is the grade for the Inner Cell Mass (ICM), and the second letter is the grade for the trophectoderm.

Here’s a general breakdown of how the letters translate to embryo quality:

  • Good quality: AA or AB
  • Fair quality: BA or BB
  • Poor quality: BC, CB, CC, or anything lower

A good-quality embryo with an “AA” or “AB” grade has the best chance of success, but even fair or poor-quality embryos can still lead to healthy pregnancies.

What is The Best Embryo Grade?

The ideal embryo grade is AA, indicating that both the ICM and the trophectoderm are high-quality. This doesn’t guarantee a successful outcome but suggests the embryo is well-positioned for the next steps in your IVF journey.

Back to blog

Read Next

Fertility Planning Community Story
What It's Like to Freeze Your Eggs: A Nurse's Personal Journey

What It's Like to Freeze Your Eggs: A Nurse's Personal Journey

Brandis Montez, AGACNP-BC, FNP-BC

Fertility nurse practitioner Brandis Montez shared her personal experience with egg freezing—twice—and offers invaluable insights for women considering this empowering option.

Embryology
Why Did My Top Grade Embryo Not Implant? Failed Transfers Explained

Why Did My Top Grade Embryo Not Implant? Failed Transfers Explained

Alease Daniel Barnes, BS

When undergoing IVF, hearing that you have a "high-quality" embryo can bring a sense of hope and optimism. But what happens when that high-quality embryo doesn’t result in a successful pregnancy? In the latest installment of her embryo grading series, embryologist Alease Barnes sheds light on this common question, breaking down why embryo grading, while helpful, doesn’t tell the whole story. What...

Grief Mental Health
Infertility During the Holidays: Tips from an Infertility Trauma and Grief Counselor

Infertility During the Holidays: Tips from an Infertility Trauma and Grief Counselor

Miss.Conception Coach

It makes sense that the holidays might look and feel different this year. Maybe we are wondering how to show up authentically when our feelings seem dismissed or not validated by some. We might wonder who closest to us has the ability to support us. It’s essential to rebalance our relationships with family and friends and learn how to align...