Temporal Evaluation of a Minimally Invasive Method of Preimplantation Genetic Testing for Aneuploidy (mi-PGT-A) in Human Embryos

Preimplantation genetic testing for aneuploidy (PGT-A) has become a useful approach for embryo selection following IVF and ICSI. However, the biopsy process associated with PGT-A is expensive, prone to errors in embryo ploidy determination, and potentially damaging, impacting competence and implantation potential. Therefore, a less invasive method of PGT-A would be desirable and more cost-effective. Noninvasive methods for PGT-A (ni-PGT-A) have been well-studied but present limitations in terms of cf-DNA origin and diagnostic accuracy. Minimally invasive pre-implantation genetic testing (mi-PGT-A) for frozen-thawed embryo transfer is a promising, less studied approach that utilizes a combination of spent culture media (SCM) and blastocoelic fluid (BF)-derived cell-free (CF)-DNA for genetic testing. This study aimed to optimize the effectiveness of mi-PGT-A for aneuploidy diagnosis by investigating the optimal temporal sequence for this protocol. SCM+BF was collected at either 48 or 72 h of culture after thawing day 3 preimplantation embryos. cf-DNA in the SCM+BF was amplified, analyzed by next-generation sequencing (NGS) and compared with results from the corresponding whole embryos (WEs) obtained from human embryos donated for research. Fifty-three (42 expanded blastocysts, 9 early blastocysts, and 2 morula) WE and SCM+BF samples were analyzed and compared. The overall concordance rate between SCM+BF and WE was 60%. Gender and ploidy concordance improved with extended culture time from 48 h (73% and 45%) to 72 h (100% and 64%), respectively. These results demonstrate that SCM+BF-derived cf-DNA can be successfully used for mi-PGT-A. Our findings indicate that longer embryo culture time prior to SCM+BF-derived cf-DNA analysis improves DNA detection rate and concordance with WEs and decreases the proportion of false positive results.