Selection of preimplantation embryos using time-lapse microscopy in in vitro fertilization: State of the technology and future directions

In this review, our aim is to give an overview of the state of the technology and clinical outcomes of time-lapse microscopy in improving embryo selection as a key step in in vitro fertilization (IVF). Using traditional incubators, morphologic assessment of the fertilized embryos is limited to snapshots at a few discrete points in time, reducing the amount of information that could potentially be obtained. Time-lapse monitoring overcomes this limitation without exposing the embryos to environmental changes. Moreover, time-lapse may introduce new dynamic markers of embryo competence as well as a versatile embryo evaluation and provides novel information regarding human embryo development. In the last few years, various algorithms have been developed correlating the kinetics of early embryo development to blastocyst formation, implantation potential, chromosomal content and live birth rate. There is not yet a universally accepted algorithm, and significant knowledge gaps remain that can provide opportunities for further research in this field.