It is very important to have knowledge of clinical cytogenetics listed below, in prenatal and perinatal medicine. 1. Basic construction. relationship between chromosome and gene. method of chromosomal analysis. cell cycle and chromosome, chromosomal abnormalities and cytological origin. 2. Chromosomal abnormalities in clinical genetics in prenatal and perinatal medicine. 3. Chromosomal abnormalities in human reproduction. 4. Accurate understanding in trisomy 18. 5. A principle in chromosome analysis -consideration for patients-.