ABSTRACT
The process of fertilization is a complex sequence of events the signs of which are perceptible as early as several seconds after sperm-oocyte fusion.1 However, the demonstration of very early signs of fertilization requires recourse to special techniques, most of which are destructive for the fertilized oocyte. Hence, since the first successful clinical application of human in vitro fertilization (IVF),2 two signs of fertilization that are detectable by non-invasive inspection of inseminated oocytes have been used: the extrusion of the second polar body and the development of pronuclei.
