damage to the embryo

[lindi]

I have the option of doing aCGH on either a 3 day embryo or a 5 day and then freeze. My RE said it depends on the embryo itself to determine which would be better. But it seems to me taking one cell on day 3 is way more damaging? What is the real percent of healthy embryos that get ruined on a removal of the cell on day 3? My lab is a very high volume highly experienced one where the frozen embryo transfer rate is very very close to fresh. Given this, wouldn't removing cells on day 5 and freezing be much better for the embryo?

[Carole]

Hi Lindi,
I am not sure what your RE means by the embryo will determine which is better.

There are advantages and disadvantages to biopsy on either day 3 or 5. If you biopsy a day 3 embryo, you'll generally get the results back in time for a fresh ET on day 5- that's good, no freezing protocol needed. A good biopsy tech can easily remove a cell without causing an obvious problem for the rest of the embryo, However, the preg rate with day 3 biopsy PGD is often reported to be lower than non-PGD cases which makes me wonder if removing one of the early cells may "weaken" the embryo in some way by either stressing the rest of the embryo or by reducing the cell numbers by 1/8 lowers the critical mass of starter cells, causing the embryo to lag slightly. If true, that may be a possible disadvantage of day 3 biopsy. I do not know of any studies about the percent of embryos that are damaged by day 3 vs day 5 biopsy. Sometimes damage isn't obvious but the embryo stops dividing and that may or may not be the reason. Internally, centers transitioning from day 3 to day 5 biopsy may collect data on survival to monitor their proficiency in transition between protocols and then on an on-going basis with the new protocol.

On the other hand, biopsy on day 5 allows more cells to be sampled which improves the accuracy of the genetic test result. The potential problem with single cell biopsy on day 3, is that it is possible that the biopsied cell is an imperfect clone (something called genetic mosaicism) and so not representative of the rest of the embryo which would cause a false diagnosis of the rest of the embryo. The downside of trophectoderm biopsy is that cells must be vitrified so the lab must also be technically proficient at doing vitrification in addition to IVF and biopsy. (It sounds like yours is if the FET and fresh rate are very close) The transfer is delayed for a later cycle, pending genetic tests. Waiting until an FET cycle allows the endometrium to be hormonally primed for implantation which some people argue improves the overall preg rate.

Everyone used to do only day 3 biopsy, then trophectoderm biopsy became available and is gaining in popularity. My opinion is that programs that have good vitrification programs will offer trophectoderm biopsy and phase out day 3 biopsy. Having said that, there are lots of babies around from PGD with day 3 biopsy too. Hopefully your RE will discuss his recommendation with you in more detail so you can understand why he thinks one approach is more beneficial for you than another. Best Wishes, Carole

[lindi]

Thanks Carole. Yes, I was led to believe that they are so good now at embryo cryopreservation at my lab that it returned almost identical pregnancy rates. And there are potential reasons to let my body rest after the egg retrieval, making freezing more attractive in my case. I wish there was some sort of data on day 3 vs 5 in terms of damage... I will talk this all over with my RE of course. So much hangs in the balance between how my body has responded to the meds and what shape its in for a transfer, and how strong the embryos are.