Intended for parents and professionals, the book explains chromosome abnormalities in lay terms and discusses the relationship of specific conditions to birth defects. Chromosomal abnormalities are defined and factors in diagnosis and recurrence are discussed. Normal chromosome reproduction processes are covered while such numerical abnormalities as mosaicism and such structural defects as deletions, translocations, and inversions are explained. Diagnosis, especially prenatal detection, is considered in detail. The final section relates chromosome abnormalities to a range of difficulties associated with birth defects. Resources (volunteer, parent, and information agencies) are discussed. The book concludes with photographs of children with chromosome abnormalities and excerpts of interviews with parents. (CL)