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Of all the factors currently available for the evaluation of embryonic potential, chromosomal status appears to be the most definitive. The debate around this hotly contested issue does not focus on the question of whether aneuploidy is detrimental to development, but on whether current preimplantation genetic testing for aneuploidy methods are capable of accurately determining whether an embryo is chromosomally normal, aneuploid or a mixture of normal and abnormal cells (i.e., mosaic). Despite the importance of aneuploidy, it is clear that this is only one factor amongst many of relevance to embryo viability, as evidenced by the fact that even the transfer of a chromosomally normal embryo cannot guarantee a pregnancy. Mounting evidence supports the hypothesis that blastocysts having unusually high levels of mitochondrial DNA detected in the trophectoderm have greatly reduced implantation potential, but there remain significant areas where further validation is necessary and where our understanding is currently inadequate. This should provide fertile ground for future research and is likely to yield some fascinating insights in the coming years.

Original publication




Journal article


Fertility and sterility

Publication Date





742 - 747


Nuffield Department of Obstetrics and Gynaecology, University of Oxford, John Radcliffe Hospital; and CooperGenomics, Institute of Reproductive Sciences, Oxford, United Kingdom. Electronic address:


Blastocyst, Humans, Infertility, DNA, Mitochondrial, Genetic Markers, Pregnancy Outcome, Treatment Outcome, Fertilization in Vitro, Predictive Value of Tests, Cell Survival, Embryo Implantation, Fertility, Pregnancy, Female, Male, Single Embryo Transfer