ABSTRACT
Assisted human reproduction is characterized by high variability in results regarding pregnancy and birth rates. In fact, in a cohort of fertilized oocytes from the same stimulation cycle, the developmental rate varies drastically, even though produced at the same time and under similar conditions [1]. This variability results in large differences in implantation potential of human embryos developed in vitro, despite similarities in observable parameters such as embryo developmental rates and morphology. Classic studies suggested that morphologic embryo quality is correlated with implantation rates, being the best predictor for the treatment outcome [2-4]. Therefore, there is no doubt that embryo morphology (determined by the number, size, and shape of blastomeres; the proportion of fragments; and the presence of multinucleated blastomeres) has some predictive value on development and implantation potential [5]. However, it is important to highlight that sometimes this conventional evaluation is not enough to get a successful pregnancy, and seemingly good morphology embryos do not always lead to implantation and birth. This could be explained by the lack of endometrial receptivity and the fact that many embryos cease to develop before implantation. For this reason, several noninvasive techniques have been proposed that may be able to detect alterations of culture environment surrounding oocytes and embryos to gain supplemental information regarding embryo viability [6-8].
