ASRM Practice Committee Releases New Document on Use of Preimplantation Genetic Testing

The American Society for Reproductive Medicine today announced that its Practice Committee has released a new report entitled “Clinical management of mosaic results from preimplantation genetic testing for aneuploidy (PGT-A) of blastocysts: a committee opinion” The report appears here in the August issue of ASRM’s flagship journal Fertility and Sterility.

The committee opinion is designed to assist clinicians as they guide their patients through the complicated decision-making that is required when preimplantation genetic testing yields ambiguous results. The first conclusion of the report is to make it clear to patients that there is not yet data to suggest that PGT-A is appropriate for all cases of IVF.

The bulk of the report deals with what conclusions can be drawn using existing testing technologies. Clinicians are cautioned that a mosaic result (the presence of more than one chromosomally distinct cell line in a single sample originating from one embryo) can be the result of a number of factors related to the testing itself and may not represent a true chromosomal problem with the embryo. Moreover, the data on outcomes regarding the health of pregnancies and children resulting from mosaic embryos is only beginning to emerge. What data there are appear to be reassuring, and thus the option to transfer mosaic embryos needs to be presented to patients, as should the potential risks.

The report identifies three main categories of risk which may be discovered: confined placental mosaicism (CPM), which is a chromosomal mosaicism detected by chorionic villi sampling (CVS) and that is largely confined to the placenta. True fetal mosaicism (TFM), also most often discovered using CVS, which if confirmed by ultrasound diagnosis poses a high risk for developmental or physical disabilities. Finally, uniparental disomy (UPD), which has also been associated with problematic outcomes.

The committee points out that as of mid-2019 there had been approximately 100 documented live births following transfer of an embryo which PGT-A testing had shown to be mosaic. However, there are significant limitations to these data including lack of long-term studies of the health of the resulting offspring. Thus, the report concludes, “While reassuring, the available outcome data must be interpreted with caution, as the risks associated with prenatally and postnatally detected mosaicism remain a possibility”.

The report strongly recommends sound, comprehensive genetic counseling for patients considering these treatments. This counseling should be based on the latest empirical studies and for now at least, ‘it is recommended that clinicians inform patients that there is currently no evidence-based method available to determine which embryos with a mosaic result have the best chance of resulting in a successful pregnancy, or which may have the lowest risks of an undesired outcome.”

Alan Penzias MD, Chair of the ASRM Practice Committee said, “PGT-A is a technique which may have a role among technologies we can offer our patients as they seek to have healthy children. We do not yet have sufficient data to endorse its universal application. When PGT-A is offered and the results are ambiguous, the committee wanted to provide some guidance for clinicians and their patients as they make difficult decisions.”

Added Catherine Racowsky PhD, President of the ASRM, “One of key roles of ASRM is to help patients and providers understand new technologies. In this report, our Practice Committee has recognized that treatment decisions must be made using the best available data, even as that data cannot yet provide completely definitive recommendations.”

For almost a century, the American Society for Reproductive Medicine (ASRM) has been the global leader in multidisciplinary reproductive medicine research, ethical practice, and education. ASRM impacts reproductive care and science worldwide by creating funding opportunities for advancing reproduction research and discovery, by providing evidence-based education and public health information, and by advocating for reproductive health care professionals and the patients they serve. With members in more than 100 countries, the Society is headquartered in Washington, DC, with additional operations in Birmingham, AL.

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