The ways in which we rely upon screening tools before and during pregnancy has recently been in the media spotlight. In January 2022, a New York Times article about the utility of noninvasive microdeletion screening sparked some interesting debates (if you're curious, some of our favorite genetic counseling thought leaders weigh in here and here).
And this public discussion is actually a great thing—an influx of testing platforms is upon us in this new era of genetic medicine, and we all need to be better equipped to make sense of when genetic testing is a good thing for us. Having these tests in the spotlight enables more of us to explore the up-sides and the down-sides to testing before we’re faced with a decision ourselves. And a public discourse is great for health professionals as well, as it enables professionals to put platform characteristics in focus, so that they are better understood, communicated, and appropriately used in clinical care.
As prospective genetic counseling students hoping to enter the field, it is an interesting time to be studying these tests, while they are being optimized and the ways in which we use them changes. We took a close look at genetic testing occurring on embryos before they are transferred in an IVF cycle. This testing, called PGT (pre-implantation genetic testing), has become more common in the US in the past decade, and as we look to the future of reproductive medicine, more intended parents are likely going to be faced with the choice of whether they want to add this testing to their IVF cycle.
Depending on the kind of testing, parents can screen for abnormal chromosome counts, specific gene conditions, or risk predictors for developing specific conditions. PGT is performed by biopsying (removing cells from) embryos early in development, typically followed by embryo freezing until results are available. Embryos identified as “low risk” can then be transferred to the uterus in the hopes of a pregnancy.
There are many things to consider when making a decision about PGT, but one of the first things patients often consider is whether doing this testing is safe for the growing embryo. We’re talking embryos here! These precious chances at life are not so easy to produce, so any hint of damage is something most fertility patients take seriously.
We analyzed the results of a study published in The American Journal of Obstetrics & Gynecology in 2021. This study was conducted from 2014-2017, linking SART data to birth certificates and maternal and newborn hospitalization discharge diagnoses in the state of Massachusetts. Considering a wide variety of maternal demographic information (including race, maternal age, education, insurance at the time of delivery, birth year, BMI, and fertility diagnosis), the authors concluded that embryo biopsy for preimplantation genetic testing did not significantly increase the odds of adverse outcomes for the carrying mother or the newborn. The following outcomes were included in their analysis: placental disorders, preeclampsia, pregnancy-induced hypertension, gestational diabetes mellitus, preterm birth, low birthweight, or prolonged maternal or neonatal hospital stay following delivery.
The authors found that the risk for such outcomes was not significantly different for pregnancies and deliveries following the use of PGT from those without PGT. Results different slightly from a previously published meta analysis that detailed a slight but significant increase in preterm birth with PGT. And though science is never absolute and additional studies would be nice to have, overall it is reassuring that current data suggest that the risk associated with PGT pregnancies is similar to risk associated with IVF pregnancies.
That said, it is important to understand that these studies did not examine the effectiveness of PGT (that's a topic for another time, and different people will prioritize the outcomes and weigh the potential pros and cons differently). Continue reading our series if you're interested in learning more on the utility of PGT!
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.