Embryo Grading Explained: What Those Numbers and Letters Mean

After egg retrieval and fertilization, your clinic will grade your embryos. These grades can feel like report cards for your future family, which makes them emotionally charged. Let's break down what they actually mean.

Day 3 vs. Day 5 grading

Embryos are typically graded at two stages. Day 3 embryos (cleavage stage) are graded on cell number and fragmentation. Day 5 embryos (blastocysts) use a more detailed system.

Blastocyst grading

A typical blastocyst grade looks like "4AA" or "3BB". Here's what each part means:

• Number (1 to 6): Expansion stage. Higher numbers mean the blastocyst is more expanded. 3+ is typically considered good.
• First letter (A, B, C): Inner cell mass (ICM) quality. This becomes the baby. A is the best.
• Second letter (A, B, C): Trophectoderm quality. This becomes the placenta. A is the best.

What grades actually predict

Here's the important part: embryo grading is not destiny. A "perfect" 4AA embryo doesn't guarantee pregnancy, and a 3BB or even a 3BC can absolutely result in a healthy baby. Grading gives your clinic useful information for transfer decisions, but it's one piece of a larger picture.

What to ask your clinic

Instead of focusing on the letter grades, ask your embryologist:

• How many embryos reached blastocyst stage?
• Which ones do you recommend for transfer or freezing?
• What does this mean for my specific situation?

Your care team knows your full medical picture. Trust their guidance alongside the data.

Note: TrackMyIVF is not a medical device and does not provide medical advice. Always consult your healthcare provider for clinical decisions.