The identification of disease before the birth of a fetus. It often implies genetic diagnosis, but identification of anatomical defects as well as assessment of fetal functions and maturity are also considered. Some of the relatively common diseases that can be diagnosed prenatally are Tay-Sachs disease, cystic fibrosis, Duchenne's muscular dystrophy, hemophilia A, congenital adrenal hyperplasia, thalassemia, and sickle cell anemia.