Procedure
Ultrasound - Ultrasound measures an area of fluid accumulation at the back of the baby’s neck called nuchal translucency (NT). This accumulation of fluid is a normal finding. Increased NT measurements, however, may indicate increased risk for chromosome abnormalities, congenital heart defects, and other genetic syndromes.
Blood test - The blood test by a fingerstick measures the levels of two proteins, free Beta-hCG and PAPP-A, which are normally found in the blood of pregnant women. The levels of these two chemicals are combined with the NT measurement and the mother’s age to provide a risk assessment for Down syndrome, trisomy 13 and trisomy 18.
Timing
11.4-13.9
weeks gestation
Detection Rate
- 91% detection of Down syndrome
- 97% detection of trisomy 18 and trisomy 13
- 40% detection of heart defects
- Does NOT screen for open neural tube defects
Miscarriage Risk
NONE
Patients of any age between gestational ages 11.4 and 13.9 weeks can be offered first trimester screening. This screening has a better accuracy in the risk assessment for Down syndrome, trisomy 13 and trisomy 18 than the triple or quad screen as well as fewer false positives. Neural tube defects can be screened for with a follow-up ultrasound at 18-20 weeks gestation with over 95% accuracy. Patients that are farther along than 13.9 weeks can be referred for a sonoscreen.
