The use of preimplantation genetic testing (PGT) both for monogenic disorders (PGT-M) and for fetal aneuploidy (PGT-A) has rapidly increased over the last decade. Based on preliminary data from the 2017 SART National Summary Report, 36% of all in vitro fertilization (IVF) cycles included some form of PGT. Given this, it is important to understand how undergoing trophectoderm embryo (TE) biopsy, the most common method of embryo biopsy used in PGT, may impact safety and efficacy. Fertility & Sterility, the journal affiliated with the American Society for Reproductive Medicine, recently published a series of articles detailing the latest research on how PGT may affect maternal and neonatal health as well as outcomes for adults conceived via this technology.
To date, research on the maternal impact of IVF with PGT has been limited, particularly in studies that isolate PGT as the lone differing factor from other pregnancies conceived via IVF. Previous research has indicated that frozen embryo transfer (FET) is associated with an increased risk of preeclampsia and placental disorders while use of a donor oocyte has also been shown to increase the risk for preeclampsia. Similarly, there are comorbidities more frequently seen with multiple gestations (twins, triplets, etc.) that may confound the results if not taken in to consideration. Without controlling for these factors, it is difficult to determine if the addition of PGT could be the cause of these complications.
Researchers from Stanford recently set out to eliminate this bias. Their study, published in 2019 in Fertility and Sterility, compared 177 pregnancies conceived via IVF with PGT to 180 pregnancies conceived with IVF alone. Within these groups, researchers were able to directly compare those pregnancies achieved via fresh vs frozen embryo transfer and singleton pregnancies to those with multiple gestation. Pregnancies conceived with a donor oocyte were removed from the analysis. All of the PGT cases underwent day 5 or 6 trophectoderm biopsy. The most common indications for PGT were screening for aneuploidy and single gene disorders.
The results of this investigation revealed a 3-fold (10.5% vs 4.1%) increased risk for preeclampsia in the IVF with PGT group. This held even when multiple gestation pregnancies were removed from the analysis. Embryo transfer method (fresh vs frozen) also did not seem to affect this risk. Preeclampsia occurs when a woman who has not previously had high blood pressure develops elevated blood pressure (140/90) and protein in her urine after 20 weeks of pregnancy. This can cause significant medical complications for the mother and baby if not treated expeditiously.
The incidence of placenta previa, or a low lying placenta covering the cervix, was higher in the IVF with PGT group (5.8%) compared to the IVF without PGT group (1.4%). The overall number of pregnancies with placenta previa was small (n=12), however, making it difficult to definitively suggest grounds for an increased concern for placenta previa with PGT.
Beyond preeclampsia and placenta previa, this study showed similar incidences of gestational diabetes, preterm premature rupture of membranes, postpartum hemorrhage, C-section, and induction of labor between both groups.
Considerations for the Future
The technology behind PGT is still relatively new, and studies on the outcomes associated with PGT are limited. This study is one of the first of its kind to definitively compare the impact of PGT on pregnancies conceived via IVF. The increased risk for preeclampsia identified in this investigation is an important consideration for clinicians. Given that this study was limited to only one institution, additional, multi-center studies to confirm this finding and determine best practices for care are warranted.
Jessica Greenwood is an independent consultant to Sharing Health Genes. As a licensed genetic counselor and digital health consultant, she 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.