The net amount of mitochondrial DNA will exponentially increase at blastocyst stage coinciding with an increases in oxygen consumption. Despite the mtDNA copy number is higher in ICM compared to TE cells the proportion of moderate and high activity mitochondria is higher in the TE cells. This also agrees with mitochondrial morphological changes in the trophectoderm cells where mitochondria are much more elongated, less matrix electrodense and have more cristae, in ICM the will be rounded and more electrodense.