Preimplantation genetic testing for aneuploidies, or PGT-A, has been a popular tool used to select embryos for transfer during In Vitro Fertilization (IVF) for decades. The technology aims to detect the number of chromosomes in an embryo, so that patients do not transfer embryos that have an abnormal count (check out this review
on the implications of chromosome errors). And since its introduction in 1995, the testing method has seen a continuous evolution in laboratory methods to culture embryos more methodically, to take small number of cells from early embryos safely, and to freeze them carefully to maintain high success rates when thawed and transferred to the uterus. The genetic technology has been refined incrementally as well, giving us ever larger DNA datasets to draw conclusions about the chromosome status of embryos.
However, there is no shortage of opinions and debate on whether it is a good idea to use PGT-A in an IVF cycle. Like any advanced technology, it's nuanced. Is it right for everyone? What are the risks? Do we really know enough about biology and what happens in the pre-implantation period of a human embryo to accurately predict its fate based on a few cells? As the technology gives us bigger datasets, does it actually change our whole way of thinking about human development?
In this opinion piece
, Dr. Norbert Gleicher breaks down the science with a very critical eye to PGT-A. He challenges the concept of mosaicism
. Could it, in fact, be a normal aspect of development for embryos to be mosaic at the blastocyst stage? And of course, receiving mosaic results
doesn’t make choosing an embryo any easier, which is kind of the point of PGT-A in the first place! Self-correction mechanisms can come into play. Testing cells destined to become the placenta is not the same as testing cells destined to become the fetus. And the technology is an expensive add-on to an already expensive treatment plan.
That said, many IVF clinicians, geneticists, and patients find it appealing
. Though it is expensive, it can reduce costs related to multiple pregnancies, failed implantations, or miscarriages. It can help avoid heartbreaking decisions about a chromosomally abnormal pregnancy. It can make it easier to plan for a specific family size, by helping to assess a patient's "inventory" of suitable embryos for transfer.
Like any big decision, there is no one-size-fits-all answer. It just depends. Depends on the age of the egg provider, how many embryos they might have to work with, their experience of pregnancy and fertility treatment, their resources, and their thoughts on disability, intentionality, fate, and risk tolerance.
Sometimes patients get frustrated at this point. Because it is not a perfect test and it does not give us a perfect answer. And we know how important these decisions and these embryos are to our patients. But realistically, this is how science works. We work with the paradigm we know, the one that has been the most supported in scientific research, and we design new tests and treatments around the working theories.
Each patient has to make trade-offs in their decision-making. Speaking to a genetic counselor about your own case can often help get you to the answer that makes sense for you.
Disclaimer: Please keep in mind that the information provided here is not meant to be a medical opinion about your specific case. The problems of every patient are unique and should be addressed by their physician or other health-care professionals in an individual conversation. You are welcome to bring up questions inspired by this blog post with your medical team. However, no one should use this blog as a source of medical care.