Assessment of embryo viability in assisted reproductive technology: shortcomings of current approaches and the emerging role of metabolomics.

The present article describes the current status of embryo assessment in assisted reproductive technologies and discusses two important issues that derive, at least in part, from our inability to adequately assess the reproductive potential of individual embryos: low implantation rates and high multiple pregnancy rates. After an overview of studies evaluating embryo metabolism as a predictor of embryo viability, use of metabolomics and additional emerging approaches for rapid, noninvasive, embryo assessment are discussed. Morphology and cleavage rate remain the mainstay of embryo assessment. A number of technologies are, however, under investigation. These include the assessment of glucose, lactate, pyruvate, and amino acid metabolism, proteomic profiling, evaluation of oxygen consumption, and most recently, examination of the metabolome. As the number of assisted reproductive technology cycles increases worldwide, improvements in the ability to quickly and noninvasively determine the best embryos for transfer remain a critical goal for reproductive medicine. Recent studies suggest that metabolomic profiling of embryo culture media may provide a useful adjunct to the current embryo assessment strategies based on morphology and cleavage rate.