Detection Rate for Trisomy 18

The first studies in which the nuchal translucency was measured and combined with beta-hCG and PAPP-A focused on the detection of Down syndrome. However, during the screening process, investigators reported detecting other chromosomal defects. This section will review the detection for trisomy 18.

Trisomy 18 is the second most common chromosomal defect that increases as a function of maternal age. Trisomy 13 is the next most common. Trisomy 18 and Trisomy 13 are usually lethal conditions in which over 95% of babies born with these conditions die during the first year of life.

The following summarizes the detection and false positive rates for Trisomy 18 and Trisomy 13.

European Studies

Spencer et al, 2003
Detection Rate: 100% (Trisomy 18 and Trisomy 13)
False Positive Rate: 5.2%

North America

BUN Study
Detection Rate: 91% (Trisomy 18)
False Positive Rate:2%