It is a pleasure to share with you some of the more recent data on prevention of the Neural Tube Defects (NTD's) through prenatal detection. The Neural Tube Defects are a consequential spectrum of major congenital malformations in the sense that one of these defects is present in every 500 births in the Unlted States with an incidence twice that in the United Kingdom. The indications for amniocentesis and prenatal studies are best looked at through the family history for the NTD's. There is an increased risk after one child is born with an NTD, and this risk increases with the birth of each affected child. In situations where there is a defect in the fetus which is open and leaking, and in 90% of the NTD's this is the case, there is an additional source of egress for the normal protein into the amniotic fluid.