Fetal chromosomes refer to the genetic material of the fetus, which is the carrier of genes. The human body generally includes 46 chromosomes, which are divided into 22 pairs of autosomes, and 1 pair of sex chromosomes, among which the sex chromosomes include two kinds, one is XX, and the other is XY, which determines the sex of the fetus. Fetal chromosome abnormality during pregnancy is a common cause of spontaneous abortion in pregnant women. It includes chromosome number abnormality and structural abnormality, which, in case of number abnormality, may lead to fetal abnormality; and in case of structural abnormality, it may cause the fetus to suffer from organic pathology. Chromosomes encode all the biological activity patterns of the fetus, and there are two common methods to detect fetal chromosomes as follows: 1. Non-invasive DNA testing: the accuracy rate of non-invasive DNA is about 95%, and the testing method is to extract 5ml of venous blood of pregnant women, from which fetal free DNA is extracted, and the possibility of three major chromosomal abnormalities can be judged by the method of biological informativeness analysis; 2. Amniocentesis: amniocentesis Amniocentesis has certain risks, but the accuracy rate can reach about 99%. 18-22 weeks is the best time to extract amniocentesis for fetal chromosome testing, because at this time the amniotic fluid contains the largest amount of viable cells shed from the fetal skin.