Noninvasive Approaches to Prenatal Diagnosis: Historical Perspective and Future Directions.

The field of prenatal screening and diagnosis has undergone enormous progress over the past four decades. Most of this period has been characterized by gradual improvements in the technical and public health aspects of prenatal screening for Down syndrome. Compared to the direct analysis of fetal cells from amniocentesis or chorionic villus sampling, noninvasive approaches using maternal blood or ultrasound have the great advantage of posing no risk of miscarriage to the pregnancy. Recent advances in molecular genetics and DNA sequencing have revolutionized both the accuracy and the range of noninvasive testing for genetic abnormalities using cell-free DNA in maternal plasma. Many of these advances have already been incorporated into clinical care, including diagnosis of fetal blood group and aneuploidy screening. The accelerated pace of these recent developments is creating not just technical and logistical challenges, but is also magnifying the ethical and public policy issues traditionally associated with this field.