Embryonal mitochondrial DNA: relationship to embryo quality and transfer outcomes

The aim was to study the association between embryonal mitochondrial DNA (mtDNA) content and embryo quality and implantation outcomes. A retrospective chart review was performed with data collected from a private IVF center database. The study population included female infertility patients with ages ranging from 31 to 38 years old, and the main outcome measures were embryo quality and transfer outcomes. From a total of 1510 blastocyst biopsies, the majority of embryos consisted of grade 1 (High), followed by grade 2 (mid), and grade 3 (poor). Embryos with higher mtDNA content were found to be of poorer quality (grade 3) relative to grades 1 and 2 (P = 0.003). Using a logistic model, mtDNA best predicted lowest and highest grades, but not mid-grade embryos. There was no correlation between mtDNA content and the subjects' age (R (2) = 0.0018). In an analysis of only euploid embryos (N = 717), there was no longer an association between mtDNA content and embryo quality (P = 0.834). There was no difference in mtDNA content between groups of embryos that did and did not implant (P = 0.53). There was also no association noted between mtDNA content and ongoing pregnancy. Compared to day 6, day 5 blastocysts contain significantly higher amounts of mtDNA (P = 0.0005), lower rates of aneuploidy (P < 0.001), and were more likely to be high-quality blastocysts (grade 1) (P < 0.001). Although the mtDNA content shows some association to the morphologic grade of an embryo, this association does not persist in an analysis of only euploid embryos. Mitochondrial DNA content also does not appear to be associated with implantation or ongoing pregnancy. Day 5 blastocysts have significantly higher mtDNA content compared to day 6 blastocysts.