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PGT-A indications and prospects explained

Dr Ángela Llaneza
Fertility Specialist, Clinica Tambre

Category:
Genetics PGS / PGT-A

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From this video you will find out:
  • What does PGT mean, and what are its main indications?
  • What are the steps followed to perform PGT?
  • How is PGT-A performed at the lab?
  • How long does PGT-A testing take?
  • What are the possible results of PGT?

PGT-A indications and prospects explained

During this webinar, Dr Ángela Llaneza, Fertility Specialist at Clinica Tambre shared an overview of PGT-A and discussed its indications such as advanced maternal age, recurrent pregnancy loss, etc. From this webinar, you will be able to learn how PGT-A can help optimize fertility treatment decisions and decrease the time for a successful pregnancy.

Definition and purpose of PGT

Preimplantation Genetic Testing (PGT) is a procedure that allows us to study the genetic composition of embryos before they are transferred into the uterus. The embryos are typically frozen during this process to enable sufficient time for diagnosis. PGT involves extracting cells from the trophoderm, which will become the placenta, leaving the embryo itself untouched and unharmed. This safe and reliable technique helps identify healthy embryos and detect genetic conditions, including monogenic diseases such as cystic fibrosis.

Indications and types of PGT

PGT serves two primary medical indications: confirming a normal karyotype in embryos and identifying disease-free carriers or non-carriers, thus ruling out potentially unhealthy embryos. Advanced maternal age is also a common reason for undergoing PGT, as older oocytes have a higher likelihood of chromosomal abnormalities. Depending on the type of results sought, there are three variations of PGT: PGT-A for chromosomal analysis, PGT-SR for balanced chromosome composition, and PGT-M for studying monogenic diseases.

Impact of Maternal Age on PGT Success

Maternal age plays a significant role in the success of PGT. As women age, the chances of producing healthy embryos decrease, leading to increased rates of aneuploidy (abnormal chromosome count) and higher miscarriage rates. By using PGT to identify chromosomally normal embryos, the chances of a successful pregnancy can be substantially increased. Recent research has shown that as long as the embryo is chromosomally normal, the pregnancy success rates remain consistent regardless of maternal age.

The PGT laboratory procedure involves extracting cells from the embryo’s trophoderm in a process known as biopsy. After the biopsy, the cells are sent to the genetics lab for extensive testing, typically using Next Generation Sequencing (NGS), which provides highly accurate results. The entire process takes around two to three weeks. While rapid results using another technique called array are possible, it is generally advisable to wait for NGS results due to its superior accuracy.

Understanding PGT Results

The PGT results can yield three possible diagnoses: euploid (chromosomally normal) embryos, aneuploid (chromosomally abnormal) embryos, and mosaic embryos containing both euploid and aneuploid cell lines. Euploid embryos can be transferred with confidence, while aneuploid embryos are not suitable for transfer to avoid potential health issues. Mosaic embryos require further genetic counseling and diagnostic assessment before deciding on transfer options.

Conclusion

In conclusion, Preimplantation Genetic Testing (PGT) is a valuable tool in modern assisted reproductive technology. It aids in identifying healthy embryos, detecting genetic conditions, and increasing the success rates of IVF procedures, especially for women of advanced maternal age. With thorough genetic testing and counseling, PGT offers new possibilities for creating healthy families.

- Questions and Answers

Do you have any positive outcome with Mosaic embryos?

I do have positive outcomes with Mosaic embryos. However, Mosaic embryos tend to have a lower implantation rate, and the success of the transfer depends on the specific chromosomes involved.

I have had 8 embryos transferred using donor eggs with no implantation. I have had extensive testing and my next recommendation is PGT-A using donor eggs Should I consider PGTA with donor embryos and donor sperm?

GTA is not typically advised with donor eggs, as the main indication is advanced maternal age. However, if you have had unsuccessful transfers, PGT-A with donor sperm might provide valuable insights into improving your chances of success.

Why isn’t PGT testing offered or recommended for all women over 35?

Overall, at present, PGT may not significantly improve the success rate in terms of overall live birth rates. While it may enhance success rates per individual embryo transfer, we need to assess its utility from a medical perspective on a population-wide basis. There is ongoing research on this topic, and its benefits may vary depending on the centre and individual cases. In private sector settings, we can discuss PGT on an individual basis, but currently, there is no strong evidence supporting its routine use in population-wide or publicly-funded treatments.  

Does your centre follow the UK’s approach of favouring single embryo transfers?  What about PGT-A for all patients?

Yes, at our centre, we also advocate for single embryo transfers as the ideal approach to achieve successful pregnancies and reduce the risk of complications. Using PGT-A on embryos helps us identify chromosomally normal embryos, improving the success rate without the need for transferring multiple embryos.  

On average, what percentage of tested embryos are found to be non-transferable? How many embryos does a woman need to test on average to have one transferable embryo?

The percentage of non-transferable embryos varies based on the woman’s age. For women over 43, the euploidy rate is less than 10%. For those around 36 years old, the euploidy rate can be around 50-60%. However, these are population-based statistics, and individual outcomes can differ. Some women may have a chromosomally normal embryo on the first test, while others may need to test multiple embryos to find a transferable one.

Can PGT-A determine the gender of the embryos (XY, or XX)?

We don’t use PGT-A for gender selection at our centre. In Spain, it is forbidden, and we focus on medical indications and improving overall treatment success.

 Can we assume that in 5 blastocyst transfers, 3 of them would be euploid or is it impossible to say? (33 year-old, karyotype is ok)

It is impossible to say with certainty. Statistics can give us an idea, but individual outcomes may vary significantly.

What is your opinion on day 7 PGT-A tested normal embryos?

It’s a controversial issue, and it falls more within the expertise of embryologists. If the embryo is normal, we would transfer it. However, the timing of the embryo’s development also plays a role. Embryos that reach the blastocyst stage on day five or early day six are generally preferred because embryos that take longer to develop might have some unique issues that could impact successful pregnancy outcomes. Ongoing research is being conducted on this topic, and we hope to have clearer insights in the coming months or years.
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Authors
Dr Ángela Llaneza

Dr Ángela Llaneza

Dr Ángela Llaneza is a Fertility Specialist at Clinica Tambre, Madrid, Spain.
Event Moderator
Caroline Kulczycka

Caroline Kulczycka

Caroline Kulczycka is managing MyIVFAnswers.com and has been hosting IVFWEBINARS dedicated to patients struggling with infertility since 2020. She's highly motivated and believes that educating patients so that they can make informed decisions is essential in their IVF journey. In the past, she has been working as an International Patient Coordinator, where she was helping and directing patients on their right path. She also worked in the tourism industry, and dealt with international customers on a daily basis, including working abroad. In her free time, you’ll find her travelling, biking, learning new things, or spending time outdoors.