Chromosome Abnormalities Detected at Prenatal Diagnosis

Abstract Prenatal diagnosis has given medical cytogenetics one of its major areas of application: from amniocentesis in the earliest days to the recent developments of noninvasive prenatal testing based upon a sample of maternal blood. This chapter explores in detail the specific diagnoses that may be made and the decisions, with particular reference to continuation or termination of pregnancy, that face those women/couples for whom a specific diagnosis has been made. The difficulties of decision inherent in a sex chromosome aneuploidy, a microarray-level rearrangement, and in the context of mosaicism are rehearsed. This discussion is offered on the background of a review of the applied embryology.