The monograph outlines modern ideas about the etiology and pathogenesis of chromosomal diseases. The main stages of human gametogenesis and embryogenesis, the contribution of chromosomal disorders to human pathology at different stages of intrauterine development and in the postnatal period, the mechanisms of occurrence of chromosomal aberrations, methods for their detection in the proembryonic and embryonic periods, the current state and existing algorithms for prenatal diagnosis of chromosomal diseases are considered. Much attention is paid to the role of prenatal diagnostics as a promising new approach for understanding the features of the functional activity of the genome and its individual elements - chromosomes at the early stages of human ontogenesis. From the standpoint of functional genomics, an idea is given of a new scientific direction - cytogenetics of human embryonic development.The monograph is intended for specialists in the field of prenatal diagnostics, primarily for cytogeneticists, medical geneticists, scientists involved in the problems of genetics - cytogenetics development, doctors and teachers of advanced training courses in medical genetics, students of medical universities and students of biological departments of universities who are interested in practical and fundamental problems of prenatal diagnosis and developmental cytogenetics.