Chromosome 4 duplication is the best option to end the pregnancy from the point of view of eugenics. Normally, the number of chromosomes in human cells (other than sperm and eggs) is 23 pairs of 46. An increase or decrease in chromosomes can lead to aberrations. An extra chromosome in one of the pairs, with an intracellular chromosome number of 47, constitutes a trisomy, which is the most common and diverse type of chromosome number aberrations in humans. A duplication of chromosome four is a type of trisomy. Due to the increase of chromosomes, especially the increase of larger chromosomes, will cause a serious imbalance of the genome and destroy or interfere with the normal development of the embryo. Therefore, the vast majority of autosomal trisomies are seen only in early miscarried embryos. A few cases of trisomy can survive to birth, but most do not live long and are accompanied by a variety of severe malformations.