Can Cell-Free DNA in the Culture Medium Predict the Chromosomal Constitution of Preimplantation Embryos? Final Results from a Multicenter Study with 2539 Blastocysts

Background/Objectives: In the last decade, non-invasive methods for aneuploidy detection have been explored. The most successful approach involves analyzing the cell-free DNA (cfDNA) released by the embryo into the culture medium. The main objective of this study is to examine the technical feasibility of this new approach called non-invasive PGT-A or niPGT-A. In addition, as an exploratory objective, the impact of the niPGT-A results on clinic outcomes will be assessed. Methods: This was a multicenter, international study that included 716 patients and 2539 blastocysts (ClinicalTrials.gov: NCT03520933). Each embryo was cultured following a specific protocol for niPGT-A. Individual spent blastocyst medium (SBM) and trophectoderm (TE) biopsy were obtained, analyzed, and compared to assess concordance. In a subset of embryos, the comparison also included an inner cell mass (ICM) biopsy. Clinical outcomes from the embryo transfers performed (all based on the TE result) were registered, and results were analyzed blindly regarding the impact of aneuploidies in the culture medium. Results: The concordance rate between SBM and TE was 79.1% (range: 74.1–82.1; cycles with autologous oocytes). This value increased to 87.0% when comparing SBM and ICM. Applying an adapted embryo culture protocol to collect the SBM for niPGT-A did not affect blastocyst quality. Analysis of the embryo transfers performed (n = 265) revealed a trend towards lower miscarriage rate in blastocysts where both TE and SBM were concordant and euploid (13.0%), compared to blastocysts with a euploid TE and an aneuploid SBM (22.2%). Conclusions: The results obtained show a high concordance between the SBM and TE biopsies. Although additional refinement of the technique would further increase niPGT-A’s performance, the results obtained support the potential use of this non-invasive approach for aneuploidy detection. The high concordance of the cfDNA present in the SBM with the corresponding ICM biopsy and the miscarriage rate observed in cases with an aneuploid SBM, despite the euploid TE results, also support niPGT-A’s capacity to assess embryo aneuploidies and its potential as a prioritization system for selecting blastocysts to transfer. This approach could hold special interest in patients with no PGT-A indications, couples that prefer not to biopsy their embryos or those who do not have access to invasive PGT-A.