By fertility experts from Spain.
In this webinar, Carolina Andrés, Embryologist, Andrology Laboratory at Clinica Tambre talked about technical terms in embryology that you need to be aware of.
It’s something that we do at the laboratory in some cases, for instance, we have some embryos are frozen, which we have not analysed genetically, and at some point, we want to analyse them. We would do the thawing procedure and then the freezing, and we can do it without any problems. Indeed, it wouldn’t be our first choice, it would be better to do the genetic analysis before, but we still can do it without any problems.
It’s true that when we see that embryos stop growing more at day-4 or 5, we would say that it’s a more male factor. However, it is important to analyse each case specifically. As I said, each case is different, and it’s important to analyse all aspects, but talking in biological terms, it’s normally associated with a male factor. As I said, we must be careful and analyse the whole case.
Our indication would be to transfer embryos that are AA, which is like the top quality. Then we would consider transferring embryos which are, for example, BA. At our clinic, we prioritize the trophectoderm quality, but as I said, each clinic has its protocol, at our clinic, we would first transfer blastocyst AA.
Mosaicism is something that we are starting to see better because of the advances in PGT technology. It is important to know that when we do the PGT, we analyse cells from the trophectoderm, so we don’t know if the aneuploidies will be in the whole part of the embryo, or just in the trophectoderm, therefore it’s a question that’s very difficult to answer.
Most mosaic embryos can be transferred, it’s something that the genetic laboratory can give you the indications for transferring such embryos and inform you about all the risks. These embryos would be transferred only after all the euploid embryos are being transferred.
We would choose the more expanded embryo. We have to take into account different factors. For us, it’s more important to check the quality, so embryos with the best quality are with letters A and B. At our clinic, we do not transfer embryos letters C or D in any of their parts. First, embryos AA would be transferred, for example, as you said, 5AA blastocyst.
Later, we would transfer, for example, BA. We would prioritize the trophectoderm quality, which is better than the inner cell mass, so we would choose BA and then maybe we would choose a blastocyst A in the inner cell and B in the trophectoderm. Finally, a blastocyst BB, as I said, the most important thing you must know from this is that a blastocyst with these letters is of very good quality, both letters A and B are very good quality blastocysts.
We’ve transferred mosaic embryos, I haven’t had many cases because normally, as I said, we prioritize transferring euploid embryos, which have a higher implantation rate. I cannot tell you a number since I don’t know, but we have transferred mosaic embryos that have developed into a healthy pregnancy.
Yes, at least at our clinic, we would choose them like that.