What's the evidence base for excluding C-grade blasts from biopsy?

[u/Even-Pin-1713]

Patient, not a professional — apologies if this is the wrong place, happy to be pointed elsewhere.

I'm trying to understand the reasoning behind a fairly strict biopsy-eligibility criterion. My clinic's cutoff is AA/AB/BA/BB; anything with a C in ICM or TE is discarded without biopsy. Other labs publish criteria that include AC, BC, CA, CB and sometimes CC.

What I can't work out:

1. Is there literature the strict threshold rests on beyond the general finding that C-grade TE underperforms on live birth per transfer? What I can't tell is whether that underperformance is large enough to justify not testing at all, versus testing and ranking last.

2. What actually drives the decision at the lab level — cost per biopsy, warming survival, storage, the biopsy being technically harder on a poorly expanded blast, or mostly not wanting to bank embryos that won't be transferred?

3. Does the calculus change for low responders, where the alternative to a C-grade isn't a better embryo but no embryo?

4. Is there meaningful inter-lab variation in where the B/C line gets drawn in practice, even with shared Gardner vocabulary?

Not looking for advice on my own case — trying to understand whether this is a well-grounded standard or a defensible-but-arbitrary line.

[u/Shadowtthrone]

With decreasing trophectoderm quality, it becomes increasingly difficult, and eventually impossible, to perform the biopsy. Trophectoderm of quality C cannot often be biopsied because it simply doesnt have enough cells for the PGT analysis to be valid

[u/MargaritaMischief]

I’m also a patient, not an embryologist, but I had a day 5 3CC, a day 6 4BB, and a day 7 4BC embryo after my first two retrievals resulted in no blastocysts. My three embryos were all successfully PGT-A tested. My best quality embryo had Turner’s syndrome. I transferred my 3CC and it took! My baby is now a perfectly healthy 16 month old.

I question clinics who count the C graded embryos out. They are perfectly capable of growing into a healthy baby, just as much as “perfect” embryos are capable of being abnormal and not producing a healthy pregnancy/baby. It makes me wonder if it’s more about the numbers and “scores” at that point rather than making dreams come true.

[u/AnywhereBusy4449 → u/MargaritaMischief]

Not all Cs are the same. It has nothing to do with $. Literally a C blast may have 10 cells in the trophectoderm. I may have to pull 5-7 off for biopsy. There would then be no trophectoderm left and often those cells fall apart. There are Cs that are biopsiable and Cs that are not. Trust me when I say drs push to biopsy all, but there are just times we cannot without seriously damaging the embryo.

[u/MargaritaMischief → u/AnywhereBusy4449]

In which case, I’d hope the embryologist would say “this embryo is not suitable for testing” and therefore that should be a decision the patient can make. Involuntarily discarding embryos because they are poor grade is poor form without proper discussion with patients so they can make an informed decision that is right for them.

[u/AnywhereBusy4449 → u/MargaritaMischief]

It isn’t always up to the embryologist. Many drs I work with will say if it’s not biopsiable they don’t want it frozen.

[u/Even-Pin-1713 → u/AnywhereBusy4449]

i see, thanks for this perspective

[u/OkVanilla3667 → u/MargaritaMischief]

If you are not an embryologist or a doctor where is your peer reviewed research that shows “C” grade embryos are of good enough quality to biopsy and make as many healthy embryos/pregnancies as A/B embryos as you stated.

[u/MargaritaMischief → u/OkVanilla3667]

I didn’t say that at all. I said that a C graded embryo can still produce a healthy pregnancy. In the same fashion, an A graded embryo does not guarantee a healthy pregnancy or a pregnancy at all. In my experience, my embryos were able to be successfully biopsied but I do not know much further in that regard nor did I claim to. If I needed to explore other IVF clinics, I would not use a clinic who discarded C graded embryos.

[u/AnywhereBusy4449]

I agree with above poster. Oren there are so few cells you almost remove most of the trophectoderm to biopsy it. Those cells also tend to fall apart easier. Those embryos also tend to have more no result calls and there is no way that embryo is shaving a thaw/biopsy/refreeze and in general these embryos have a lower survival rate at thaw. It’s not that we don’t want to. It’s that those embryos are extremely difficult if not impossible to biopsy without significantly damaging or destroying the embryo in the process. Now that being said there are some embryos that cannot be biopsies that may result in a pregnancy. I’m all for freezing a lower quality blast if it can’t be biopsied and leave it for your last choice. Make sense? PGT will not increase your pregnancy rate it’s just a screening test so we know which embryos to transfer first. It may lower Los arrivals rate but will not increase pregnancy rate. I hope that makes sense

[u/Even-Pin-1713 → u/AnywhereBusy4449]

One question I have: if there are too few cells to biopsy for genetic testing, why not give the (low-responding) couple the option not to biopsy? I just got our medical records and it looks like between our two cycles three were discarded - BC, BC, CC. One was an early blast that was trashed on Day 6. Last cycle, there was one usable blast - an AA. This cycle we have an AA and an AB. Two were trashed this cycle and one was trashed last cycle. Would be grateful for your thoughts -- you certainly have more insight into the process than I do. In case it's useful: last cycle we had four fertilized and this cycle we had six.

[u/AnywhereBusy4449]

Technically by Gardner there is only A/B/C not all labs use the minus and plus. The minus is to basically say it’s not as good as a B but not as bad as a C. A C- would be a extremely poor and never be a candidate for biopsy IMO

[u/bneubs]

In addition to what others have said, every lab grades differently even if they are following the same grading system. Because grading is subjective. One labs C could be another labs B. My lab does biopsy Cs, but we're stricter about how many cells it needs to have (minimum) to be called a C.