The present invention relates, e.g., to a method for predicting the embryonic progression of a preimplantation embryo, comprising measuring in the insemination medium (IM) in which an oocyte was fertilized and subsequently incubated in vitro, thereby generating a pre-implantation embryo, at 18-24 hrs post fertilization, the levels of nitric oxide metabolites (NOx) in the insemination medium (IM), wherein a level of NOx of at least about 1.3 μM indicates that the preimplantation embryo is likely to progress to the blastocyst stage by culture day (CD) 5.
