How much have we learned from time-lapse in clinical IVF?

Can the time-lapse system (TLS) identify the best embryo for transfer? Although there are several studies that support this hypothesis, more research is required to improve the quality of the current evidence and also to assess live birth rate, miscarriage, stillbirth or clinical pregnancy in order to choose between a TLS or conventional incubation. In addition, although some authors report on effectiveness and safety in the use of TLS monitoring of embryo development in vitro, other authors that have not found relevant differences between the two systems for the culture and subsequence embryo selection. On the other hand, TLS has emerged as a novel technology and has been introduced into clinical practice in many laboratories to perform embryo morphology evaluation and study developmental kinetics in ART. However, most studies only assess blastocyst formation or implantation rate as the primary end-point and additional data are required, for example, about live birth, monozygotic twinning rates and health problems. Furthermore, the features of populations studies are varied; for example, female and male age, seminal characteristics and female factor. The embryo culture conditions and culture medium used also vary. For this review, a search of PubMed was conducted to retrieve relevant studies regarding use of TLS in embryo incubation and selection, and compare them with standard embryo culture and evaluation.