Exploring mitochondrial DNA content as a novel biomarker to improve embryo implantation potential: A review

According to the society of assisted reproductive technologies (SART), the top fertility clinics in North America have reported overall pregnancy rates of up to 50% in good prognosis patients. Although new techniques in advanced reproductive technologies have begun to emerge in the twenty-first century, including time-lapse monitoring of embryo development, analysis of metabolites in embryo culture media, and the use of artificial intelligence in morphometric embryo grading, currently chromosomal status obtained via pre-implantation genetic testing for aneuploidy (PGT-A) appears to be the most definitive in evaluating embryonic potential. Yet still, in most clinics, approximately 30% of euploid or chromosomally normal embryos fail to achieve a viable pregnancy resulting in stress and anxiety for patients, repeat cycles, and increased cost of treatment. Recent literature suggests that blastocysts with an increased mitochondrial DNA (mtDNA) ratio have greatly reduced implantation potential, however, there exists controversial studies which do not report a relationship. This review summarizes the current literature on utilizing mitochondrial DNA as a possible biomarker for embryo implantation, highlights the reasons for inconsistencies in some studies and suggests possible improvements to the study design of future mtDNA ratio research.