It is a subfield of clinical genetics and gynaecology that exemplifies the effective integration of theoretical and clinical medicine milestones in its history include development of cytogenetics, Molecular genetics.
Prenatal diagnosis strictly comprises all diagnostic modalities aimed at gaining information about the embryo or fetus. In narrower usage it refers to prenatal identification of genetically determined disease and their disposition.
In contrast to PGD, PID is carried out on embryonic cells prior to establishment of pregnancy where one of the blastomeres from 8 cell stage is removed for molecular cytogenetic analysis.