* Author Topic: Can anyone explain IVF terms such as grade one embryos?  (Read 11126 times)

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Offline clare2

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Despite going through my 4th IVF cycle, I'm still not sure what 'grade one' embryo means. Also, what do four-cell, six-cell etc mean?

How many cells in an embryo is good on day 3 or day 5?

I'm having ET tomorrow so maybe I should just ask my doctor!



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    Offline chandelle

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    Hi there, there isn't a standard grading system so you have to check with your clinic how they rate the embryoes. at mine it was from 1 to 4, with 4 being the best.

    four-cell, etc. represents how many cells the embryo has. after fertilisation the cells should keep dividing - by day 2 you want 4 cells and by day 3 they should have at least 8 cells. i'm not sure about day 5 but assume it's 32 cells - at that stage it's called a blastocyst.

    good luck!!!

    Offline ☼♥ Minxy ♥☼

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    Here's some info on grading and cell division...

    "Day 1 Check eggs for fertilization (the presence of two pronuclei or PN's)
    Day 2 Embryos at the 4-cell or more stage of development
    Day 3 Embryos at the 8-cell or more stage of development
    Day 4 Embryos at the compacted morula (16-32 cell) stage
    Day 5 Embryos at the blastocyst stage of development

    ...Critical points in development are (1) fertilization, (2) 4 to 8 cell stage and (3) morula to blastocyst stage.

    With regards to grading, some clinics use the reverse scale so that Grade 4 is best...you would need to check with your own clinic (ours uses Grade 1 as best) and some clinics don't grade at all...

    Numeric grading systems for multicell embryos usually have 4 levels (this showing Grade 1 as best):

    Grade 1: even cell division, no fragmentation
    Grade 2: even cell division, small fragmentation
    Grade 3: uneven cell division, moderate fragmentation
    Grade 4: uneven cell division, excessive fragmentation

    Blastocysts are graded differently with a number and two letters.

    The number refers to the degree of expansion of the blastocyst (1 is the least expanded, 6 is the most expanded). The first letter (A,B, or C) refers to the quality of the inner cell mass (the part of the blastocyst that is going to be the baby) and the second letter (A, B, or C) refers to the quality of the trophectoderm (the part of the blastocyst that is going to be the placenta).

    Sometimes the laboratory uses the reversed scale where a grade 4 embryo is equivalent to a grade 1 embryo on the above scale. Check with your lab

    And here's some more info...


    However, lower grades and less cells doesn't necessarily mean that won't implant, just as higher grades can't guarantee success...

    This website shows pictures of the different embryos and uses the reverse grading where grade 4 is best...


    and here's another interesting website...


    Hope that helps.

    Take care

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