ABSTRACT
The pronuclear (PN)-stage embryo is the rst stage of life where the genetic material of both female and male is visible as pronuclei and when fertilization is initiated. Although it is possible to judge the morphology of the oocyte and the spermatozoa by itself, the PN stage is the rst event that allows for morphology rating of the new life by various small details that are indicative for the future of the embryo.
