17Study question 18 Can mitochondrial DNA (mtDNA) levels in trophectodermal cells of the blastocyst predict the 19 blastocyst quality, ploidy status, implantation rate and clinical outcomes? 20 Summary answer 21 mtDNA levels in trophectodermal cells of the blastocyst do not associate with the blastocyst 22 quality, ploidy status, implantation potential and clinical outcomes, but can differentiate between 23 aneuploid and euploid blastocysts.24 What we already know 25 mtDNA levels in the trophectodermal cells have been suggested to be associated with blastocyst 26 morphology, ploidy and implantation rates, and has been proposed as biomarker to access 27 blastocyst quality and predict clinical outcomes. However, discrepancies exist if mtDNA levels 28 could serve as a marker for the same.29 Study design and duration 30