Non-invasive chromosome screening for embryo preimplantation using cell-free DNA

Abstract Preimplantation genetic testing (PGT) is a widely adopted screening method that can be performed to identify and select embryos with normal ploidy; however, PGT relies on embryo biopsy, that is, polar body, embryo cells, or trophectoderm biopsy, to obtain embryonic DNA, increase its technical limitations. Studies have indicated that biopsy may have an influence on the quality and development of embryos, and increase the chance of abnormal epigenetic modifications. Therefore, non-invasive PGT (niPGT) detection of cell-free DNA (cfDNA) has gradually become a hot research topic in the field of assisted reproduction. Studies showed cfDNA could be detected in blastocyst fluid and spent culture medium (SCM) in vitro cultured embryos. The cfDNA collection requires less skill and makes lower risk to embryos. Some studies have been conducted to evaluate the feasibility of SCM-based niPGT approaches. When comparing the ploidy consistency of cfDNA in SCM, its consistency to the conventional PGT for aneuploidies results fluctuated widely, it is critical to recognize the factors influencing accuracy. These contradictory results may be related to factors such as the difference in SCM sampling methods and sampling time, and the definition of consistency. In this review, we aimed to comprehensively summarize how researchers use embryonic cfDNA to conduct niPGT detection. It also systematically reviews the factors affecting the accuracy of the test and its underlying issues, as well as prospective applications. We hope to provide a basis for future niPGT research and a useful reference for the standardized operation of niPGT that can be widely applied in clinical practice.