The present invention relates to a process for the non-destructive determination of gender, developmental stage and/or viability of an avian embryo in an egg, comprising (a) detecting at least a first developmental marker compound selected from sugars and/or amino acids, precursors and metabolites thereof in an egg at a time period of from the beginning of the incubation of the egg until the hatching (b) measuring the amount of the at least first detected developmental marker compound, and (c) comparing the amount to a base line established for male and female, developmental stage of the embryo, and/or alive and deceased or non-developed embryo, to determine whether the embryo is viable, male and/or female, and/or the developmental stage of the embryo.
