In science truth ultimately wins, and PGT-A is no exception

A review of the 2021/2022 PGDIS Position Statement on the transfer of mosaic embryos

The practice of preimplantation genetic testing for aneuploidy (PGT-A) in association with in vitro fertilization (IVF) since 2016 has been mostly directed by three highly controversial guidance documents issued by the Preimplantation Genetic Diagnosis International Society (PGDIS). Because these documents are so influential on worldwide IVF practice, the most recent one is here the subject of a detailed review, again revealing important misrepresentations and internal contradictions. Most importantly, however, this most recent guidance document still does not prevent the non-use and/or disposal of large numbers of embryos with substantial pregnancy and live-birth potential and, therefore, continues to propagate an IVF practice harmful to many infertile women.

Previously reported and here added cases demonstrate euploid pregnancies followed by PGT-A as "mosaic" as well as "aneuploid" designated embryos

BACKGROUND

After the longest time opposing all transfers of embryos by preimplantation genetic testing for aneuploidy (PGT-A) diagnosed as "chromosomal-abnormal," the field has over recent years slowly been moving toward selective transfers of by PGT-A as "mosaic" diagnosed embryos, but is still rejecting transfers of embryos by PGT-A defined as "aneuploid."

METHODS

Upon review of the literature, we report published cases of euploid pregnancies following transfers of PGT-A as "aneuploid" diagnosed embryos and add several additional, ongoing cases at our center.

RESULTS

Among the published cases from our center, we identified seven euploid pregnancies from "aneuploid" embryos, four of which preceded the PGT-A industry's 2016 switch from binary "euploid" - "aneuploid" reporting to "euploid," "mosaic," and "aneuploid" reporting. That those four cases post 2016 PGT-A definition involving "mosaic" embryos, therefore, cannot be ruled out. Since then, we recently established three additional ongoing pregnancies from transfers of "aneuploid" embryos which still await confirmation of euploidy after delivery. A recent fourth pregnancy from the transfer of a trisomy 9 embryo miscarried before a fetal heart. Outside our own center's experience, the literature revealed only one additional such transfer, involving PGT-A as a "chaotic-aneuploid" diagnosed embryo with six abnormalities, leading to normal euploid delivery. In reviewing the literature, we furthermore demonstrate why current PGT-A reporting that differentiates between "mosaic" and "aneuploid" embryos based on relative percentages of euploid and aneuploid DNA in a single trophectoderm biopsy of on average 5-6 cells, is biologically non-sensical.

CONCLUSION

Basic biological evidence and a clinically still very limited experience with transfers of PGT-A as "aneuploid" labeled embryos demonstrate beyond reasonable doubt that at least some "aneuploid" embryos can lead to healthy euploid births. Therefore, this observation establishes beyond reasonable doubt that the rejection of all "aneuploid" embryos from transfer reduces pregnancy and live birth chances for IVF patients. Whether (and to what possible degree) pregnancy and live birth chances differ between "mosaic" and "aneuploid" embryos, remains to be determined. The answer will likely depend on the aneuploidy(ies) of an embryo and to what degree percentages of "mosaicism" in a single, on average 5/6-cell trophectoderm biopsy can reflect the ploidy-status of a complete embryo.

Elucidating the PGT-A paradox: marginalising the detriment relegates the benefit

The hypothetical analysis presented offers insight into the effect of maternal age and protocol on the cost-effectiveness of PGT-A to reduce the risk of clinical miscarriage without materially jeopardising the chance of a first live birth when attempting to transfer every suitable embryo one at a time. Reflecting current practices, the diagnostic accuracy of PGT-A is sensitive to the prevalence of embryos with chromosome aneuploidy which increases with advancing maternal age, and the power of the test to discern a non-viable embryo is higher for older women and sensitive to protocol. PGT-A is effective to mitigate (reduce not eliminate) the risk of clinical miscarriage; however, excluding embryos with intermediate copy number results from transfer is detrimental to accomplishing a first live birth from a full cycle. Paradoxically, the number of blastocysts needed to marginalise the detriment is achieved only for some younger women (≤ 40 years) who are less likely to benefit by avoiding pregnancy loss; this also makes PGT-A an expensive adjuvant. The paradox can be avoided by excluding from transfer only embryos with a 'uniform' aneuploid test result, which mitigates the risk of miscarriage for all women with the potential to be cost-effective for those > 40 years.