A Prospective, Observational, Multi-center, International Study to Validate a Non-invasive Preimplantation Genetic Test for Embryo Aneuploidy in the Spent Culture Media (niPGT-A).

Human embryos have higher aneuploidy rates (20-80%) than other species. A considerable proportion of these aneuploid embryos have the ability to reach the blastocyst stage. However, depending on the aneuploidy type, some will fail to implant in the uterus, while others will implant but will be unable to carry out early embryonic development (miscarriage), or very rarely, result in liveborn children with specific abnormalities. It is therefore important to identify aneuploid embryos. The identification of aneuploidies is especially important in embryos from patients with higher aneuploidy risk such as those with advanced maternal age (AMA), recurrent implantation failure (RIF), or recurrent miscarriage (RM).

PGT-A technique analyse the full chromosome content of the embryo with high sensitivity and specificity but requires an invasive biopsy to obtain embryonic material for the genetic analysis. Thus, non-invasive methods to replace the existing invasive testing method would be useful in the improvement of maternal and fetal safety.

Recently, there have been many research advances in the field of genetic testing. Cell-free DNA (cfDNA) has been observed in spent embryo culture media. The origin of the cfDNA at the blastocyst stage remains unknown and this has encouraged different research groups to carry out analysis of the spent culture media.

Various studies were initially carried out to detect specific genes associated with monogenic disorders (MTHFR9, HBA1/HBA210, SRY11). Recently, non-invasive PGT-A has been developed, with highly variable results on the concordance rate (3.5%,59.1%, and 85.7%, 30.6%). The chromosomal status of the embryo from the DNA present in the spent culture medium was compared to the one obtained following the standard protocol using trophectoderm biopsy. The difference in the reported results can be related to the different methodologies applied because different amplification and detection methods -aCGH or NGS- were used. Moreover, the concordance rates were defined differently on each study, i.e. aneuploid results in spent culture media and trophectoderm biopsy could be considered concordant despite of showing not the same aneuploid chromosomes.

The impact of culture conditions in the efficiency of the non-invasive approach has been thoroughly investigated. There could be influence of these relevant factors: external contamination from laboratory personnel or equipment, contamination with maternal DNA from granulosa cells (MCC) and mosaicism threshold for diagnosis..