This chapter reviews the basic principles of genetic counseling relevant for patients considering undergoing prenatal diagnostic techniques. Genetic counseling is a communication process which deals with the problem associated with the risk of occurrence of a genetic disorder. An appropriately trained person helps to comprehend the medical facts, including the diagnosis and available management, to educate how heredity contributes to the disorder, and the risk of recurrence in relatives. Invasive procedures performed during pregnancy differ from procedures performed in any other medical setting since there are two patients potentially at risk, the mother and the fetus.