The present invention provides a noninvasive discrimination method of chromosomal heteroploidy of a fetus, the method including a step of analyzing DNA of a candidate cell of a nucleated red blood cell isolated from maternal blood, in which the fetuses are fetuses classified into any one case selected from monotocous, monochorionic monoamniotic twin fetuses, monochorionic diamniotic twin fetuses, and dichorionic diamniotic twin fetuses based on results of ultrasonic inspections and the number of candidate cells of nucleated red blood cells to be used for analyzing the DNA is optimized based on the classification, and a noninvasive discrimination system of chromosomal heteroploidy of a fetus.
