ASSISTED REPRODUCTION TECHNOLOGIES
Embryonal mitochondrial DNA: relationship to embryo quality
and transfer outcomes
Amber M. Klimczak
Lucia E. Pacheco
Kelsey E. Lewis
Jon P. Richards
William G. Kearns
Antonio F. Saad
John R. Crochet
Received: 20 November 2017 / Accepted: 25 February 2018 / Published online: 5 March 2018
Springer Science+Business Media, LLC, part of Springer Nature 2018
Purpose The aim was to study the association between embryonal mitochondrial DNA (mtDNA) content and embryo quality
and implantation outcomes.
Methods 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.
Results 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
= 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).
Conclusion 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.
Keywords Mitochondrial DNA
Maternal age is the most important determinant of fertility, and
with many women today opting to delay childbearing,
infertility rates are on the rise . As women age, declines
in oocyte quantity and quality termed Bovarian aging^ results
in diminishing pregnancy success [2, 3]. While many ovarian
aging factors have been examined, recent studies suggest mi-
tochondrial DNA (mtDNA) may play a key role [4, 5]. Unlike
nuclear DNA (nDNA), mtDNA is a small genome approxi-
mately 16.5 kb in size inherited through the oocyte cytoplasm.
It encodes genes in the electron transport chain, where most of
cellular energy is created via oxidative phosphorylation .
Because sufficient energy supply is needed to obtain embryo
viability, the role of mtDNA in infertility has been investigated
The primordial germ cell houses approximately 200 copies
of the mtDNA. Throughout development, the copy number
increases and decreases until ultimately a mature oocyte con-
tains greater than 200,000 copies—this number is variable [8,
9]. As women age, the rate of oocyte mtDNA with a deletion
Accepted as poster presentations at the ASRM 2017 Meeting in San
Antonio, Texas, and PCRS 2018 Meeting in Indian Wells, California.
* Amber M. Klimczak
Department of Obstetrics and Gynecology, The University of Texas
Medical Branch, 301 University Blvd, Galveston, TX 77555, USA
AdvaGenix, Rockville, MD, USA
Center of Reproductive Medicine, Houston, TX, USA
Department of Gynecology and Obstetrics, Johns Hopkins
University School of Medicine, Baltimore, MD, USA
Journal of Assisted Reproduction and Genetics (2018) 35:871–877