Blastocyst embryo grading

Just wanted to share some information on how blasts are graded.  My embryos were graded 4BB and this is what they looked like (this is not my embryo):

Image of 4BB grade blastocyst

which is not the best but good.  This is based on the Gardner grading system.  Not all RE’s use this rating system but a lot do.

Definition of a blastocyst:

Blastocyst Development and Blastocyst Quality Grading (or scoring)

  • There are 3 distinct parts to a blastocyst – the two cell types and the fluid cavity (see picture above)
  • As development of blastocysts progresses, cells in the 2 components divide and the fluid cavity enlarges
  • With continued blastocyst development the embryo expands, the shell thins, and it hatches from its shell
  • Blastocyst implantation into the lining of the uterus can then begin

Our IVF clinic and many others that do blastocyst culture and transfer use a blastocyst scoring system originally developed and published by Dr. David Gardner in the late 1990’s. Dr. Gardner is well known for being first to develop a commercially available embryo culture media system that supported high rates of viable blastocyst development. There are other grading systems for blastocysts , but this one is most widely used.

The Gardner blastocyst grading system assigns 3 separate quality scores to each blastocyst embryo:

  1. Blastocyst development stage – expansion and hatching status
  2. Inner cell mass (ICM) score, or quality
  3. Trophectoderm (TE) score, or quality
Blastocyst development and stage status

Blastocoel cavity less than half the volume of the embryo


Blastocoel cavity more than half the volume of the embryo


Full blastocyst, cavity completely filling the embryo


Expanded blastocyst, cavity larger than the embryo, with thinning of the shell

5 Hatching out of the shell
6 Hatched out of the shell
ICM grade

Inner cell mass quality


Many cells, tightly packed


Several cells, loosely grouped


Very few cells

TE grade

Trophectoderm quality


Many cells, forming a cohesive layer


Few cells, forming a loose epithelium

C Very few large cells

My name is Cindy

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Posted in IVF
8 comments on “Blastocyst embryo grading
  1. newtoivf says:

    thank you, this is really helpful

  2. V says:

    How many do you have?

  3. Thanks for posting that, my clinic uses that grading system and I never knew what it meant. The embryos that became my 2nd and 3rd children were both 5AA. We had one that was discarded after thawing as it didn’t have an inner cell mass.

  4. oc15 says:

    one thing i found strange was our embryologist never told us any of the “grades” of our blastocysts. as they reached day 5, it seems the dr. and embryologist just like referring to them as “beautiful blasts”. i wonder now if that was their code for a BB grading? i guess i could call and find out all of their grades… although, i don’t want to be that neurotic mom already 😉

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