RICHARD T. HULL
Examination of the fetus in utero probably first occurred almost 100 years ago when an X-ray picture was taken of a dead fetus. However, prenatal screening and diagnosis as we think of them now have been available routinely to certain groups of women and selectively to others since the late 1970s. Amniocentesis and the other technologies of prenatal screening and diagnosis currently in use provide access to fetal cells and amniotic fluid and enable the visualization of the developing fetus. These technologies allow detection before birth of all recognizable chromosomal variations, many selected developmental malformations, over 150 biochemical disorders, and fetal sex; the list continues to expand, and the techniques are being applied earlier and earlier in pregnancy.
Examination of amniotic fluid obtained by needle aspiration was first attempted in the late 1920s. Initially amniocentesis was employed as part of the effort to manage RH disease, in which blood type incompatibility between fetus and mother results in a deadly condition called erythroblastosis fetalis. Management consisted in total transfusion at birth in the so- called blue baby, so amniocentesis was performed in the last trimester of pregnancy. Advances in the 1960s and beyond in somatic cell genetics have permitted diagnosis of genetic diseases and diseases resulting from