ABSTRACT
During the last decades, various studies have described characteristic sonographically detectable features of most chromosomal abnormalities. In the first trimester, increased nuchal translucency thickness is a common sonographic finding of major aneuploidies. Risk evaluation by maternal age and measurement of nuchal translucency has emerged as a highly effective screening method with detection rates of 70% to 80% for autosomal trisomies, for a screen positive rate of 5% (1-3). In addition, the sonographic demonstration of the presence of a nasal bone allows a further decrease of the calculated individual risk (4).
