In this session, Dr Carmen Morales, PhD, a Genetic Counsellor and Laboratory Coordinator at Reproclinic, Barcelona, has discussed PGT-A, process, its benefits, recommendations and results.
If the lab conditions are not good, you can indeed have a lot of abnormal embryos, not only chromosomally abnormal but also morphologically abnormal embryos. If the conditions are not optimized, they can cause abnormalities in the embryos, and they can be a source of aneuploidy. For that reason, the protocols in an IVF lab should be checked, and they have to follow very strict protocols. So yes, the conditions can influence the quality of the embryos.
Very young women 16-17-year-olds can indeed have a higher rate of aneuploid embryos, but it’s also true there is a higher risk of Down syndrome when mothers are very young. However, this is a result of this study shows, I don’t exactly know how many patients are 28 years old, I added this as an example. Most probably, if you are using the graphics from other published papers, possibly the percentage will be lower.
There is not a very big difference between 27 or 29, so I think before the age of 30 years old, the results will be best. I cannot tell you a specific age based only on the graphic of one paper.
Mosaicism means you have different cell lines, for example, you have one cell line that it’s completely normal, four to six chromosomes, and one cell line, there is trisomy 21. If you are only analysing one cell, you cannot detect different cell lines. If you are randomly taking the normal cell, then you are going to have a normal result of this embryo. If you, by chance, are taking the cell that has trisomy 21, the diagnosis of this embryo will be trisomy 21. We are only analysing one cell that is recommended on day-3 because more can damage the embryo development. We are not able to detect mosaic by a FISH or any other technique because we are only testing one cell.
If a laboratory is doing the biopsy and all the embryos are of very poor quality, then most probably the embryos will be chromosomally abnormal, and then you will have very bad results. You would think this lab is giving me very bad results, no you are giving them very bad samples, so it’s a conjunction of both things. You need very good conditions in the IVF lab, you need to choose the embryos we are going to biopsy to have good laboratory results.
You can see a lot of variabilities even in the same genetic laboratory that is receiving samples from different IVF labs, there can be great variability between the results. It’s the same with IVF centres, they are different, they have different conditions, different patients. Some centres specialize in very difficult cases. Then the probability of abnormality in the embryos is higher than in others where they are doing IVF to everybody, and they have very good prognosis patients. It’s not only the genetic laboratory, it’s everything that it’s giving you good or bad results.
There are two tendencies. Some professionals say since we can detect abnormal embryos in all ages, even in young patients, even though the percentage is not very high, it can be 20%, let’s do PGT-A to all patients. On the other hand, we have another group of professionals that don’t see an advantage in doing that, and they decide to offer PGT-A only for a specific group of patients.
According to published data, PGT-A is improving the outcomes mainly in patients over 35 years old. In young patients, including egg donors, if there is no other factor like a severe factor, published data didn’t show any improvement in the results. In my opinion, there are different policies, different tendencies, but I would recommend PGT-A only to specific groups that we know are at higher risk to see the benefit of this test.