Amniocentesis without visible abnormalities to the naked eye, meaning that the results of amniocentesis, which do not show any obvious abnormalities by the recognition of chromosomal images after cell culture, indicate that disorders with an abnormal number of chromosomes in the fetus can be excluded. However, genetic disorders as well as metabolic disorders and malformations of the neural tube cannot be excluded. Amniocentesis is a common method of prenatal diagnosis, and the optimal time for amniocentesis to extract amniotic fluid is between the 16th and 24th weeks of gestation. Chromosome cultures are performed to determine the presence of chromosomes in the baby, but amniocentesis cannot completely rule out that the fetus has some structural abnormality, such as congenital heart disease. At this time, it is necessary to combine with the 23-26 weeks of the examination (ultrasound) to see if the fetus has any structural malformations. In addition, pregnant women over 35 years of age, pregnant women who have delivered abnormal fetuses in the past, and those who have a high risk of Down’s syndrome or non-invasive DNA during pregnancy are recommended to undergo amniocentesis during pregnancy to clarify the presence of fetal chromosomal disorders.