Is there still a use for sonographic fetal evaluation in the era of widespread noninvasive prenatal tests?

Joseph Hasson, Igal Wolman

Ultrasound Unit in Obstetrics and Gynecology, Lis Maternity Hospital, Tel-Aviv Medical Center, Tel Aviv, Israel

The second trimester ultrasound examination evaluates the fetus for structural malformations, and also searches for sonographic markers of fetal Down syndrome. The main markers include increased nuchal fold, short humerus and femur, echogenic intracardiac focus, pyelectasis, hyperechoic bowel, and any major abnormality. The absence of any marker reflects a 60%–80% reduction in the prior risk of trisomy 21 based on advanced maternal age or serum marker screening risk.¹ The presence of sonographic markers, either singly or in combination, raises the baseline risk as calculated for each individual marker. Many studies have attempted to establish the sensitivity and specificity of these various ultrasonographic markers in order to allow adjusting the risk for trisomy 21, and therefore the need for genetic amniocentesis, depending on the presence or absence of these markers. Some found the average sensitivity of these markers to be 31% for short femur, 33% for short humerus, 32% for short femur and humerus, 32% for nuchal fold thickening, 7% for echogenic bowel, and 71% for short ear length.² Nicolaides also addressed the performance of screening tests for trisomy 21.³ He combined data from two major series and published the following likelihood ratio for Down syndrome according to the presence of the sonographic markers as follows: nuchal fold 9.8; short humerus 4.1; short femur 1.6; hydronephrosis 1.0; echogenic focus 1.1; echogenic bowel 3.0; and any major defect 5.2.³