Promises and pitfalls of first trimester sonographic markers in the detection of fetal aneuploidy

Abstract

First trimester sonographic markers are the only markers achieving detection rates above 50% in the prenatal detection of fetal aneuploidy. Although potentially they are the best markers, some concerns have arisen about its clinical application. Pitfalls may be due to inability to examine the markers, incorrect assessment, or incorrect interpretation of the findings. Markers may be unable to be examined due to maternal (maternal body habitus, previous surgery) or fetal reasons (incompatible fetal position or fetal movements). Causes of incorrect interpretation may be insufficient image magnification, incorrect caliper placement (nuchal translucency), incorrect insonation angle (nasal bone), venous contamination (ductus venosus), or arterial contamination (tricuspid regurgitation), among others. Venous contamination in ductus venosus waveforms may mimic an abnormal blood flow when it is normal, and the opposite can also occur. Finally, incorrect interpretation of a substantially increased nuchal translucency may lead to a false impression of an ominous fetal prognosis or may be confounded with a cystic hygroma.

Influence of gravidity and foetal gender on the value of screening variables in the first trimester of pregnancy

“…Probably, the training of echographers has a greater clinical impact, as confirmed by Borrell [15], who documented that inexperienced echographers characteristically underestimate the NT score. In our service, the training process in NT measurement over the course of the study, with the progressive incorporation of new echographers, is reflected in Table 1, i.e.…”

Ductus Venosus in the First Trimester: Contribution to Screening of Chromosomal, Cardiac Defects and Monochorionic Twin Complications

“…Contamination by the inferior vena cava or hepatic veins may mimic a reversed a-wave and, conversely, contamination by the umbilical vein may hide an absent ductus venosus a-wave. According to Borrell [13] , in the contamination by inferior vena cava or hepatic veins, two V-shaped lines are seen, while in true reversed flow the line delineated by maximum velocity follows a single continuous V-shaped line, crossing zero. In contamination by the umbilical vein, a 'truncated' V line is seen ( fig.…”

“…30°; (6) the filter should be set at a low frequency (50-70 Hz) so that the a-wave is not obscured, and (7) the sweep speed should be high (2-3 cm/s) so that the waveforms are spread allowing better assessment of the a-wave [12,13] .…”

First‐trimester screening and its impact on uptake of diagnostic testing

“…In order to reduce the false positive rate to 0.5%, the achievable detection rate would still be 90.5% (Cicero S et al, 2003). Although several studies have shown the effectiveness of using fetal nasal bone as an ultrasound marker, fetal nasal bone assessment has not become a standard part of FTS due to the difficultly in interpretation and low specificity (Borrell, 2009). …”