Low mosaic aneuploid embryos reclassified as euploid

[Haf05]

For anyone out there with low mosaic embryos in the freezer. I had two low mosaic embryos in the freezer which i had PGTA tested last year. I was told today that based on new data from a recent study by the genetics laboratory that did the PGTA testing , the low mosaic aneuploid embryos have been reclassified as aneuploid (!!) This is the information i was given:

"A recent study ... looked at outcomes following the transfer of low mosaic aneuploid embryos. The results from this study suggest that:

• The outcomes of transferring low mosaic aneuploid embryos are no different to the outcomes of transferring euploid embryos.

• Low mosaic aneuploid embryos have the same chance as euploid embryos of leading to a live birth. The miscarriage risk for low mosaic aneuploid embryos is similar to that for euploid

embryos.

• In cases where a low mosaic aneuploid embryo was transferred and genetic testing was carried out during pregnancy or after birth, the chromosome abnormality identified in some of the cells by PGT-A was not subsequently found in the developing baby/child. This might be because the abnormality was only ever present in ‘placental cells’ (where the biopsy was taken from) and not in foetal cells, or it might be that the embryo is somehow able to ‘correct’ the abnormality as the embryo develops.

This data has caused us to reconsider how we report low mosaic aneuploid results. We now report low mosaic aneuploid embryos as euploid embryos and, like all euploid embryos, they are recommended for transfer...without requiring genetic counselling first."

It was really lovely news.

[MollyRobs]

thanks for sharing Haf05 as we have one LoS mosaic so this is interesting for our situation. Is there any way of you finding the study so we can share it with our embryologist? Thank you

[Haf05 in reply to MollyRobs]

In the info pamphlet we've been given the study is cited as: Capalbo et al. (2021). Mosaic human preimplantation embryos and their developmental potential in a prospective, non-selection clinical trial. Am J Hum Genet. 2;108(12):2238-2247.

[Tryingtostaycalm]

  Haf05 we had the same call this week with our 2 low mosaic we have in the freezer which have been reclassified to the Normal Status! It was so lovely to hear!

The only thing I’m slightly concerned about is we had a genetic counselling appointment to discuss them a few months ago and having the information now means I have knowledge I can’t ignore (if that makes sense?). When we spoke to the genetic counsellor she said one of them had a missing chromosome and the only risk if they transferred it would be failure to implant or a miscarriage, but if we went past 12 weeks it would be fine. The 2nd embryo had an additional chromosome and there was some risk of this implanted and they would recommend additional tests. But based on this new ruling they are both normal and if we didn’t have the genetic counselling appointment would be none the wiser.

This also makes me questions PGS testing now if I’m honest!

[Haf05 in reply to Tryingtostaycalm]

We also had genetic counselling, with similar advice, and i completely understand where you are coming from. I guess the answer may be in the third bullet above:

"In cases where a low mosaic aneuploid embryo was transferred and genetic testing was carried out during pregnancy or after birth, the chromosome abnormality identified in some of the cells by PGT-A was not subsequently found in the developing baby/child. This might be because the abnormality was only ever present in ‘placental cells’ (where the biopsy was taken from) and not in foetal cells, or it might be that the embryo is somehow able to ‘correct’ the abnormality as the embryo develops."

I am currently 11 weeks with a euploid embryo, but if it comes to the point where i have to transfer one of the two embryos which were formerly low mosaic, i would probably have a chat with the embryologist.