Understanding PGT-A: Expert Series

With Beatriz Rodriguez-Alonso, PhD

This blog was created and written by Shelby Carpenter, with the assistance, support, and scientific expertise of Beatriz Rodriguez-Alonso, PhD. We thank Dr. Rodriguez-Alonso for her commitment and contributions to the field of fertility medicine.

IVF journeys can be… complicated. Suddenly you’re receiving an overload of information that might be brand new to you! Maybe PGT-A (Preimplantation Genetic Testing for Aneuploidies) is included in your treatment package, in which case you’re probably wondering: what information will I receive for the cost? Or your clinic might offer PGT-A as an add-on and put the decision in your hands… we’ve witnessed these internal debates (to the patients who change their mind in the final hour – we are talking to you!).

We spoke with the amazing Beatriz Rodriguez-Alonso, PhD, a Scientific Advisor at Igenomix, to provide you with some information on PGT-A. Dr. Rodriguez-Alonso is an exceptional advocate of patients pursuing IVF, with the belief that education is key to making informed decisions while you grow your family. Here are excellent insights on PGT-A from the expert herself.

So, what is the purpose of PGT?

“PGT-A is utilized in the in-vitro fertilization (IVF) process to assist in selecting embryos with the best potential for successful pregnancies. Before transfer, specialists screen an embryo biopsy for chromosomal copy number changes. Human cells typically have 23 pairs of chromosomes (46 in total), with half inherited from the egg and half from the sperm. Euploid embryos, characterized by the typical chromosome copy number, are the most likely to grow and develop into a healthy baby. Aneuploidy, a deviation from the typical copy number, can hinder pregnancy and is a leading cause of spontaneous miscarriages. It could also lead to birth defects and cognitive impairment in liveborn babies. PGT-A is essential for identifying any extra or missing chromosomes in embryo biopsies, providing crucial information for IVF practitioners and patients, and guiding decisions on which embryos to transfer.”

Since the likelihood of aneuploid embryos increases with the age at egg retrieval, your doctor is likely to strongly suggest this test if you’re in your late thirties or older. But do not shy away from this information if you’re a younger patient! Embryo quality can vary and if you’re interested in having the most information available, you should look closely at this option.

Another fun fact about PGT-A? The chromosome analysis will tell you if there is a ‘Y’ chromosome present. Yep, you’ll be able to see the sex of your embryo!

Having the information from PGT-A will help you and your doctor plan your treatment by prioritizing the transfer of embryos that are most likely to result in a healthy pregnancy, and avoiding the transfer of embryos that have a low chance of implantation.

How does it work?

When your embryo(s) reaches a particular stage of development, the embryologists will take a small biopsy from the trophectoderm (the cells right beneath the outer shell that will form the placenta) of each embryo and send the sample out for chromosome testing. They will then pop your embryos into the cryopreservation tanks while you await your results! The result time varies but can take a few weeks.

Risks of embryo biopsy are believed to be low, and while the quality of your treatment varies from clinic to clinic, it’s important to know that in rare cases, this biopsy could impact the integrity of your embryo. You should speak to your doctor to learn more about the risks.

PTA Benefits

By selecting embryos with typical chromosome copy numbers, PGT-A increases implantation rates and reduces miscarriage rates. This is particularly advantageous for high-risk groups, including women with a history of recurrent miscarriage or recurrent implantation failure, those who have experienced a prior pregnancy with a chromosome abnormality, and men with abnormal sperm analysis, as they may have a higher percentage of abnormal embryos.

Moreover, the comprehensive screening capacity of PGT-A, which includes the identification of various viable aneuploidies (Trisomy 13, Trisomy 18, Trisomy 21, Monosomy X, Trisomy XXY, Trisomy XYY, and Trisomy XXX), ensures a decreased chance of pregnancies or babies with chromosomal abnormalities.

Awareness of limitations

There are a few misconceptions about PGT-A, and Dr. Rodriguez-Alonso is going to help us iron them out. For starters, “PGT-A does not increase the cumulative live birth rates. In other words, it does not enhance the chances of a live birth when using all fresh and frozen embryos obtained from a single ovarian stimulation cycle”. This is because, although PGT-A provides information to prioritize embryo selection for transfer, it does not impact the quantity or quality of embryos obtained.

While PGT-A provides a lot of great information, “PGT-A is not a substitute for routine prenatal screening and diagnostic testing.” This is important! PGT-A is a chromosome analysis and does not mean that you can skip out on your prenatal screening. It provides excellent information for the beginning stages of conception but doesn’t replace the other information you will need to support a healthy pregnancy.

Also, it’s vital to know that not all embryos are ‘eligible’ for PGT-A testing. This means that your embryologists might be concerned about performing a biopsy based on your embryo(s) grade. For example, if you have an embryo developing a bit slowly or not showing great inner cell mass, your embryologist may avoid a biopsy to preserve the embryo's quality and eliminate PGT-A’s small risks.

PGT-A, like any screening test, has limitations. We encourage you to discuss the risks, benefits, and alternatives of PGT-A testing with your genetic counselor, reproductive endocrinologist, or the person ordering the test. As Dr. Rodriguez-Alonso reminds us, “Screening embryos for aneuploidies is an option but not everyone needs it.” Speaking with your doctor about the recommendations for your treatment is the best starting point. Remember that resources are available to find out more.

Meet The Expert

Beatriz Rodriguez-Alonso holds a bachelor's degree in Biology and a master's in Human Reproduction. She earned her PhD in Reproductive Biology from University College Dublin with a Marie-Sklodowska Curie fellowship in 2019. Dr. Rodriguez-Alonso started as a Clinical Embryologist in an IVF clinic, where she developed a passion for research, leading to her pursuit of a PhD. Her doctoral research focused on embryo-maternal communication during preimplantation stages. After completing her PhD, she became a Postdoctoral research fellow in Dr. Rajkovic's laboratory, contributing to projects in Reproductive Genomics. Currently, she serves as a Scientific Advisor at Igenomix, specializing in reproductive genetic services. Dr. Rodriguez-Alonso has made notable contributions to the IVF field, with multiple publications, presentations, and awards, including the "Ángel Bayo Prize" for the best article in the International Journal of Andrology. She was also a finalist for the MSCA Awards in the "Outreach of the MSCA Project" category and has been involved in various roles, such as an ESHRE young ambassador and a member of the Board of Governors of the Student Group of IETS.

Interested in more information on PGT-A? Follow Beatriz Rodriguez-Alonso, PhD on Instagram