Does PGT Increase the Risk for Birth Defects and Adverse Outcomes?

by | Apr 30, 2019
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Couples who choose to undergo in vitro fertilization (IVF) with preimplantation genetic testing (PGT, also known as preimplantation genetic diagnosis or PGD) are motivated by the desire to prevent the transmission of a genetic disease to their pregnancy. For many of these couples, family or personal history of the genetic disease is their only risk factor. Natural conception may be an option for them, so evaluating the safety of the IVF + PGT process is of significant concern. There is a risk for birth defects and adverse outcomes like prematurity, low birth weight, or stillbirth in any pregnancy, but it is important to understand how this risk may be affected by IVF and PGT before deciding to proceed with this option for conception.

While most babies conceived via IVF are healthy, the procedure has been associated with higher rates of obstetric complications like high blood pressure during pregnancy as well as preterm delivery and low birth weight. In addition, some studies show an increased risk for birth defects and other disorders that may impact neurological development like autism. It seems that the vast majority of the risk can be attributed to the increased chance for having multiples (twins, etc.) due to transfer of more than one embryo. As the practice of single embryo transfer becomes more common, recent data suggests that the risks for poor perinatal outcomes like prematurity and low birth weight in these pregnancies are no different than those in a singleton pregnancy conceived naturally. However, the increased risk for adverse outcomes like birth defects and neurodevelopmental disorders remains, suggesting that other factors, like a history of infertility or use of intracytoplasmic sperm injection (ICSI), may also play a role. For couples who elect IVF with PGT due to a history of a genetic condition, it is unclear if their pregnancies would be at increased risk or not.

What are the risks of PGT?

PGT involves the biopsy of potential embryos to determine if they carry the genetic condition in question. PGT is therefore considered to be a more invasive process to the embryo than IVF alone. Given this, it has been suggested that PGT itself may increase the risk for birth defects and adverse outcomes. Initial studies indicated that PGT did not increase the risk for birth defects, but did confer some increased risk for adverse outcomes like prematurity, low birth weight, and stillbirth. However, it is challenging to directly associate those outcomes with PGT as these studies also included women who underwent preimplantation genetic screening (PGS), suggesting that some of these pregnancies could have been complicated by maternal age or a history of infertility.

A large review published in 2018 of over 400 pregnancies conceived via IVF with PGT only offers reassuring results. This study concluded that PGT itself does not appear to be an independent risk factor for birth defects or adverse outcomes. Rates of birth defects in the study cohort were comparable to the general population and while the incidence of low birth weight was high (20% of the children born), the rate was similar to that seen in IVF pregnancies as a whole.

Given these considerations, the informed consent process is critical to ensuring a complete understanding of all of the risks before deciding on the best course of action. Emily Mounts, MS, CGC, Director of Genetic Services at ORM Fertility says,

“Every patient undergoing IVF with PGT should be counseled on the safety of these procedures by their physician and/or genetic counselor. While the data we have currently is reassuring, new studies on IVF/PGT outcomes are always being published.”

Considerations for the Future

The technology behind PGT is still relatively new, and studies on the outcomes associated with PGT are limited. As individuals conceived via this technology grow older and as their number increases worldwide, additional research is warranted to confirm what, if any, risks are associated with PGT.

As a licensed genetic counselor and digital health consultant, Jessica Greenwood works with health-related organizations looking to deliver memorable messages of health in the digital space. Mrs. Greenwood started her career in a clinical role, working for eight years as a preconception and prenatal genetic counselor before transitioning to industry. Mrs. Greenwood completed a year-long certificate program in Digital Health Communication at Tufts University that spearheaded her work in digital health. She now consults with health-related organizations, assisting with the creation and execution of a digital strategy including the development of health literate patient-centered educational materials. Mrs. Greenwood earned a Bachelor of Science degree from North Carolina State University with a minor in Genetics and a Master of Science in Genetic Counseling from the University of North Carolina at Greensboro.

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