Will noninvasive methods surpass invasive for assessing gametes and embryos?

The need to identify the most viable embryo following in vitro fertilization (IVF) was established early in the history of human IVF. The stalwart of identifying the best embryos has been morphology. Other techniques have however seen wide acceptance, including the use of preimplantation genetic screening, even though concerns exist over the invasive nature of the technique. Alternatively, noninvasive assessment technologies have tried to determine an embryo's viability through measurements of factors in the media or by imaging of the embryo. We present data showing that the metabolic blueprint of an embryo is linked to viability, and argue that analysis of metabolic function, using either spent medium or by novel microscopies, could provide the basis for selecting the embryo with the highest viability. This review therefore asks, "Will noninvasive methods surpass invasive for assessing gametes and embryos?" We examine the current state of research on noninvasive technologies, including novel optical methods, and conclude noninvasive embryo viability assessment will assist in embryo selection for transfer.