PPV vs NPV Fetus with Down Syn Test

PPV vs. NPV Fetus with Down Syn. Test shows Increased risk 42 Test shows Low risk 8 Total 50 True Positive False Negative Fetus NOT with Down Syn. 1250 23700 24950 False Positive True Negative Total 1292 23708 25000 Sensitivity: 42/50 = 85% (detection rate) 15% of women with a trisomic 21 fetus will be missed by the test Positive Prediction Value: 42/1292 = 3. 25% 96. 75% of women with an increased risk result will NOT have a DS baby Negative Prediction Value: 23700/23708 = 99. 96% of women with a low risk result will NOT have a DS baby

Echogenic Intracardiac Focus • 88% are only in the left ventricle • 5% are only in the right • 7% are biventricular • likelihood ratio of 2. 8 for fetal aneuploidy • has not been associated with congenital heart disease • When isolated, no further ultrasounds, including echocardiography, are required (other soft markers, maternal age, and maternal serum screening results, right/left/ biventricular)

Choroid Plexus Cysts • small cysts (>3 mm) found in the choroid plexus within the lateral cerebral ventricles of the developing fetus at 14 to 24 weeks’ gestation • 50% in fetuses with trisomy 18 • Only 10% of fetuses with trisomy 18 will have CPCs as the only identifiable sonographic marker on ultrasound screening • The number/distribution/size does not change the risk. • the risk when isolated, the likelihood ratio for trisomy 18 is 7 • Isolated, age<35, low risk screening result • Isolated, age>35/positive screening result (18, 21) NO further action! fetal karyotyping (cell-free)