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What do embryo grades mean?

Embryo grades assess quality based on cell number, fragmentation, and blastocyst development. A Day 5 blastocyst graded 4AA has excellent expansion (4), top-quality inner cell mass (A), and top-quality outer cells (A). While higher grades suggest better odds, many healthy babies come from lower-graded embryos.

Last updated: December 2025

Understanding Embryo Grades

Embryo grading helps embryologists select the best embryos for transfer. Use this guide to understand what your embryo grades mean and set realistic expectations about how grading relates to success.

Build Your Blastocyst Grade

Select each component to see what your Day 5 embryo grade means:

4AA
Excellent Quality
Expansion (4):Expanded blastocyst - cavity larger, thinning shell
Inner Cell Mass (A):Many cells, tightly packed - becomes the baby
Trophectoderm (A):Many cells forming cohesive layer - becomes the placenta

Blastocyst Expansion Grades (1-6)

The first number indicates how expanded the blastocyst is:

GradeDescription
1Early blastocyst - cavity less than half the embryo
2Blastocyst - cavity half or more of embryo
3Full blastocyst - cavity fills embryo
4Expanded blastocyst - cavity larger, thinning shell
5Hatching blastocyst - emerging from shell
6Hatched blastocyst - completely out of shell

Cell Quality Grades (A, B, C)

Inner Cell Mass (ICM)

Develops into the baby

A:Many cells, tightly packed
B:Several cells, loosely grouped
C:Few cells

Trophectoderm (TE)

Develops into the placenta

A:Many cells forming cohesive layer
B:Few cells forming loose layer
C:Very few cells

Day 3 Embryo Grading

Day 3 embryos (cleavage stage) are graded on cell number and fragmentation:

CellsFragmentationGradeMeaning
8 cells<10%ExcellentIdeal cell number with minimal fragmentation
6-8 cells10-20%GoodOn track with acceptable fragmentation
4-6 cells20-35%FairSlower development or more fragmentation
<4 cells>35%PoorSignificantly delayed or highly fragmented

Remember

Embryo grading is subjective and varies between embryologists. A "good" embryo at one clinic might be graded differently at another. Focus on your clinic's assessment of your specific embryos rather than comparing grades online. Many healthy babies come from "average" looking embryos.

Track Your Embryos

Use IVFPath to record your embryo grades, track their development day by day, and keep notes from your clinic about each one.

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Frequently Asked Questions

Medical Review: IVFPath Medical Content Team • Last reviewed: December 2025

Disclaimer: This guide explains common embryo grading systems. Grading conventions vary between clinics. Ask your embryologist or clinic to explain how they grade and what your specific grades mean in their system.