What Is Embryo Grading—and What Does It Mean for Your IVF Journey?
If you’re going through in vitro fertilization (IVF), chances are you’ve heard your care team mention “embryo grading.” And if you’ve found yourself Googling what those grades mean—or worrying whether a grade defines your chances of success—you’re not alone.
At Tennessee Fertility Institute (TFI), we believe in giving patients not just answers, but context. Embryo grading can be helpful, but it’s only one part of a much bigger picture. Here’s what you need to know about how embryos are graded, what those grades mean (and don’t mean), and why it’s best not to read too much into them.
What Is Embryo Grading?
Embryo grading is a tool embryologists use to evaluate embryos as they grow in the lab after fertilization. Typically performed between days 5 and 7, when the embryo reaches the blastocyst stage, grading involves closely examining the embryo under a microscope and assigning it a “score” based on how it looks.
It’s a bit like a report card—but one that’s far more nuanced than it may appear.
What Do Embryo Grades Measure?
Embryo grading generally looks at three main features:
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Expansion: How far the embryo has developed or expanded
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Inner Cell Mass (ICM): This is the cluster of cells that becomes the baby
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Trophectoderm: This will develop into the placenta
Grades may look like this: 4AA, 3BB, 5AB, etc.
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The number reflects the expansion stage
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The first letter refers to the ICM quality
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The second letter refers to the trophectoderm quality
It’s easy to assume that higher grades = better outcomes. But that’s not always the case.
Every Clinic Grades Differently
Here’s something we want to make crystal clear: every clinic has its own grading system.
While there are general similarities, embryo grading is not a universal standard. It’s an internal lab tool—used differently depending on the training, experience, and protocols of each embryology team. What’s graded as a “4BB” in one lab might be graded slightly differently in another.
Even here at TFI, we are constantly refining and reevaluating how we approach grading as technologies evolve and our understanding deepens. That’s why it’s so important not to get too caught up comparing grades across different clinics—or even between cycles.
So… Does a Higher Grade Mean a Better Chance of Pregnancy?
Not necessarily.
Embryo grades help us prioritize which embryos to transfer or freeze, but they don’t determine your outcome. Many other factors affect the likelihood of pregnancy, including:
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The genetic health of the embryo (especially if you’ve done genetic testing)
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The uterine environment
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Maternal age and hormonal balance
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Timing and technique of the transfer
We’ve seen lower-graded embryos lead to healthy babies—and highly graded embryos that don’t implant at all. That’s why embryologists look at the overall potential of an embryo, not just its letter grade.
What If My Embryos Have Different Grades?
That’s completely normal.
It’s common for patients to have embryos with a range of grades from the same cycle. Your doctor and embryologist will look at the full picture—grades, development timing, and any available genetic information—to help determine the best embryo to transfer or freeze.
If you’ve done PGT-A (preimplantation genetic testing for aneuploidy), the genetic profile may matter more than the visual grade when choosing an embryo.
The Bottom Line: Your Embryo Is More Than a Grade
Embryo grading gives us valuable insight, but it doesn’t define your future. At TFI, our embryologists use grading as one part of a much larger decision-making process—guided by science, experience, and care.
We know how tempting it can be to go down internet rabbit holes trying to decode every detail of your embryo report. But we encourage you to pause, breathe, and talk to your care team before jumping to conclusions. We’re here to explain what your specific grades mean, how they fit into your treatment plan, and what next steps make the most sense for you.
Have Questions About Your Embryo Grades?
Whether you’re in the middle of a cycle or just starting to explore your options, we’re here to support you with personalized guidance and expert care. At TFI, you’re more than a number—and so is your embryo.
Contact us today if you’re ready to schedule an appointment! Let’s take the next step together.