Diagnostic ultrasound ( PDFDrive )

1098 PART IV Obstetric and Fetal Sonography
A
B
C
D
FIG. 31.7 Major Congenital Anomalies in Trisomy 21 Detected in the Second Trimester. (A) Ventriculoseptal defect (VSD). Four-chamber
view of the heart with a ventriculoseptal defect (arrow) demonstrated with color low Doppler. (B) Atrioventricular (A-V) canal. Four-chamber
view of the fetal heart demonstrates a complete A-V canal. Note the abnormal “lattening” of the mitral and tricuspid valves into a common A-V
valve (arrows). (C) Duodenal atresia. Axial scan through the fetal abdomen shows a double bubble. (D) Ventriculomegaly. Axial scan through
the cranium of a fetus with trisomy 21 shows dangling choroid in fetus with ventriculomegaly. Note that calipers were placed on the ventricles
during scanning but are not in the appropriate location or scanning plane for measuring the ventricles.
TABLE 31.2 Trisomy 21: Likelihood
Ratios (LRs) of Cluster of Markers
Markers (#) LR 90 LR 91
0 0.36 0.2
1 2 1.9
2 9.7 6.2
3 115.2 80
fetal head, across the thalami and angled posteriorly to include the
cerebral peduncles, cerebellar hemispheres, and cisterna magna
as well as the occipital bone. he measurement is made from
the surface of the occipital bone to the surface of the skin edge
(Fig. 31.8). Care must be taken not to angle below the occiput
because this will lead to spuriously large measurements. Initially,
a measurement of 6 mm or greater was considered abnormal;
however, 5 mm was later determined to be a more sensitive
threshold, with little change in the speciicity. 99 Interobserver
variability for this measurement is small (1 mm), establishing