PGT-A – chromosomal aneuploidies diagnosis

Carmen Morales, PhD
Genetic Counselor and Laboratory Coordinator at Reproclinic, Reproclinic

Category:
Genetics PGS / PGT-A, Miscarriages and RPL

pgt-a-diagnosis
From this video you will find out:
  • What is PGT-A and how the test is performed?
  • What is a Karyotype?
  • How many chromosomes are in a karyotype?
  • What are the chromosomal abnormalities?
  • What is the impact of chromosomal aneuploidies on human reproduction?
  • When PGT-A is recommended?
  • What is mosaicism?
  • What are the benefits or possible downsides of PGT-A?

When is PGT-A recommended and how is it performed?

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.

When is PGT-A recommended and how is it performed? - Questions and Answers

Is there a known cause for miotic issues in the embryo causing mosaicism? Can there be a problem with the culture in the lab?

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.

If I’m correct, on the graph from Fransiak et al presented, younger women have a higher aneuploidy rate than, e.g. 28-year-old woman, which showed the lowest rate. In egg donation, would a 28-year-old woman be the best for an egg donor?

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.

Was it possible to detect mosaicism with the old technique using FISH and day-3 biopsy?

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.

Your data shows Santi’s the best at PGT-A. What lab do you use in Spain?

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.

What about egg donor recipients? Is there any benefit from PGT-A to improve pregnancy outcomes?

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.

Authors
Carmen Morales, PhD

Carmen Morales, PhD

Dr Carmen Morales is a Genetic Counselor and Laboratory Coordinator at Reproclinic, Barcelona, Spain. She obtained her degree in Biology in 2000 at the University of Barcelona. She started working at the Hospital Clinic of Barcelona as a Specialist in the Biochemical and Molecular Genetics Service, where she developed her research in molecular cytogenetic. In 2011, she obtained her PhD in human genetics at the University of Barcelona. Since 2012, she is working in Reproductive Genetics. She was a teacher in the Master of Genetic Assessment (Universitat Pompeu Fabra, Barcelona) and published more than 20 papers in peer-reviewed international journals, different chapter books and collaborated in several research projects. Since 2012, she has accreditation in Human Genetics by the Spanish Association of Human Genetics.
Event Moderator
Caroline Kulczycka

Caroline Kulczycka

Caroline Kulczycka is an International Patient Coordinator who has been supporting IVF patients for over 2 years. Always eager to help and provide comprehensive information based on her thorough knowledge and experience whether you are just starting or are in the middle of your IVF journey. She’s a customer care specialist with +10 years of experience, worked also in the tourism industry, and dealt with international customers on a daily basis, including working abroad. When she’s not taking care of her customers and patients, you’ll find her traveling, biking, learning new things, or spending time outdoors.

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