Last week, we discussed the realities of medical history and embryo adoption. It may have left some of you wondering, “Why would I need to be more flexible with my preferences concerning medical history when embryologists now have the ability to test embryos for certain genetic markers before a transfer is performed?”
Preimplantation genetic diagnosis (PGD) is a procedure used prior to an embryo transfer to help identify genetic defects within embryos created via IVF. This serves to prevent certain genetic diseases or disorders from being passed on to a child. PGT-A, or preimplantation genetic testing for aneuploidies, is another genetic test performed on embryos before transfer (previously called pre-implantation genetic screening, or PGS). The goal of PGT-A is to provide information about embryos’ genetic health with hopes of improving the chance of achieving pregnancy.
Usually, reproductive endocrinologists will advise families to pursue these tests if they are over the age of 35, are carriers for a genetic disease, or have had recurrent miscarriages.
These tests have been touted by RE’s as the end-all-be-all of pregnancy success through IVF, and strongly urge families to pursue genetic testing on their embryos. As a result, a recurrent myth has been perpetuated throughout the assisted reproductive technology community:
"PGD and PGT-A are accurate indicators of an embryo’s risk of genetic abnormalities and can eliminate the risk of producing a child with a genetic condition. It also increases the chance of achieving pregnancy success."
To put it simply, this is not true.
In fact, most embryo adoption programs in the United States have a policy that prohibits adoptive families from testing their embryos due to this myth. Let us break down the science and research surrounding PGD and PGT-A to see where these claims fall short.
One peer-reviewed article from 2016 found that some embryos created via IVF are mosaic embryos. In other words, the embryos contain normal and abnormal polar body cells. And this is more common than previously thought! Developing embryos have an amazing ability to correct abnormal cells as they grow. If only the abnormal polar body cells are selected for testing during PGD or PGT-A, then the whole embryo could be mislabeled as abnormal, even though it could grow into a perfectly healthy baby. Dr. Norbert Gleicher, MD, who performed the 2016 research study, estimated that only 30% of PGD tests show accurate results!
The conclusion which was drawn from this study is that it is still possible to give birth to a completely healthy baby even if the embryo tested “abnormal.” This video features Dr. Gleicher, explaining embryo mosaicism and how they can distort PGD & PGT-A test results.
Another peer-reviewed article showed current techniques for PGD or PGT-A have not been shown to improve live birth rates after a transfer. There are many families who adopt PGD-tested embryos, only to have none of those embryos result in a baby. There are also instances of families transferring embryos that were said to have a low chance of pregnancy success result in a healthy baby. Perhaps in time newer techniques may prove useful; however, neither PGT-A nor PGD guarantees a pregnancy. In fact, there is growing concern that newer genetic tests are being offered clinically without studies to support their utility. Some have even argued that clinicians are influenced by the financial gain in offering these tests regardless of the accuracy of the results, although this is just pure speculation.
What should you take away from this? One, embryos are complex and have intricate designs. Just because an embryo tests “abnormal” does not mean the resulting baby will show genetic anomalies. Second, families who are pursuing embryo adoption should keep in mind that adopting PGD or PGT-A tested embryos will not increase your chances of pregnancy success.
If your adoption agency has a policy against PGD/PGT-A testing, most often you are still given an extensive medical background on the placing family and the children born from the embryos. Many times, you are even able to see pictures of the family! And if you are pursuing an open adoption, you will always have up-to-date knowledge on the placing family’s medical history.
To learn more about embryo donation and adoption, visit EmbryoAdoption.org.