Prenatal Diagnosis of Trisomy 21

The triple test can detect 80 percent of trisomy 21 pregnancies.

Ultrasound examination can decrease the sensitivity of the triple test.

The most common biochemical marker associated with trisomy 21 is increased nuchal fold thickness.

Choroid plexus cysts are a common finding in normal fetal development.

Cystic hygromas are a fatal congenital anomaly.

The false-positive rate of the triple test is 10 percent when ultrasound examination is not used.

The 'double-bubble sign' is a characteristic of duodenal stenosis.

Incurving of the fifth finger is a common finding in normal fetal development.

First-trimester screening using ultrasound measurement of nuchal translucency is a highly effective screening test for trisomy 21.

Renal pelvis dilation is a soft marker for trisomy 21.