Chromosome abnormalities occur in about one in a hundred people, and present complex challenges for medical geneticists and genetic counselors. In addition to identifying chromosomal abnormalities, genetics professionals must explain the "unexplainable," helping families understand why chromosome disorders occur and how likely they are to occur again. Chromosome Abnormalities and Genetic Counseling is the definitive guide to navigating chromosome disorders and clinical questions posed by the families they impact. It incorporates the latest advances in molecular technologies and prenatal diagnosis, while also revisiting the classical understanding of chromosomal pathology; the well-known trisomies, deletions, and duplication syndromes; and ways in which these may arise de novo or occur in the setting of a parental chromosome rearrangement. This new edition includes three entirely new chapters on copy number variants, chromosome abnormalities associated with selected phenotypes, and ethical and counseling issues. Completely updated and still infused with the warmth and voice that have made it essential reading for professionals across medical genetics, the 6th edition of Chromosome Abnormalities and Genetic Counseling represents a leap forward in clinical understanding and communication. It is more than just a reference text; it is a holistic guide to thinking about these disorders, even as our technical understanding of them continues to evolve.