Screening for chromosomal abnormality.

Screening for fetal abnormalities has become one of the most high profile health care issues of modern times. This issue is predicated on major advances in health care technology that permit wider detection of fetal anomalies, including the development of more advanced biochemical markers and improvements in ultrasound imaging. The effectiveness of these screening methods and their rational application is a point of great controversy, and is the cause of considerable unease in clinical obstetrical practice. This article reviews the general concepts of fetal screening for fetal chromosome abnormalities and then focuses on certain aspects of ultrasound screening that are particularly controversial. The scientific basis for each ultrasound finding (e.g., nuchal translucency) is reviewed, as well as the frequently divergent clinical experience with the finding. Finally, a plea is made for the development of a more scientific database for fetal ultrasound screening, and the setting of fetal screening guidelines for practicing physicians based on diagnostic accuracy and cost-effectiveness.