Morphokinetics of In Vitro-Derived Embryos-A Lesson from Human and Bovine Studies

Embryo transfer has become a major method to improve fertility in both humans and cattle. The current review focuses on predicting an embryo with a high developmental competence and high potential to establish pregnancy. One way to evaluate the embryo quality is to assess its morphology. However, this approach provides only limited and inadequate information. Using a time-lapse system allows a continuous monitoring of embryonic development. Here we introduce the main morphokinetic parameters and discuss their potential to predict embryo viability, implantation, pregnancy, and live birth. Special attention is given to the association between the transcript's profile and the embryo developmental potential; normally cleaved embryos differ in their profile from their abnormally cleaved counterpart; synchronously and asynchronously cleaved embryos, which are both defined as suitable for transfer, differ in their transcript profile. Recently, the advancements and wide use of time-lapse systems led to the development of algorithms for embryo selection. This technology is already implanted in human in vitro fertilization units, but it is not yet used for domestic animals. The authors believe that combining information from both the human and bovine morphokinetics might reveal the benefits of using a time-lapse system to select embryos with good potential for transfer.