Early Screening for Risk of Down Syndrome
This screening program is based on results from the FASTER Trial. This was a nationwide study conducted through the National Institutes of Health. The University of Colorado Health Sciences Center was a principle participant in the Trial.
Early screening allows women and their families to make better decisions about whether to have invasive procedures. The program has two stages, which combine ultrasound information and blood analysis. The first stage involves a brief ultrasound examination and analysis of a blood sample. The second stage involves collection and analysis of a blood sample only. A detailed explanation of these stages is provided below.
The First Stage:
The first stage involves an ultrasound examination performed between 11 weeks – 13 weeks and 6 days of pregnancy. This ultrasound will measure the length of your fetus and the “nuchal translucency.” The nuchal translucency is a fluid filled space beneath a membrane that is found on the back of the fetus’ neck. We will also look for the nasal bone (often absent in a fetus suspected to have Down syndrome).
In approximately 70% of pregnancies with Down syndrome, this nuchal translucency will be thicker than expected. After this examination, you will be informed as to whether the results are reassuring or less so. During your visit blood will also be drawn. This blood sample will be sent to a special laboratory that will determine the levels of two analytes (chemicals) and then will combine these levels with the ultrasound findings. Results of this first trimester test will be available in 3-5 business days. The results will be called to you by a member of our staff and then faxed to your physician. They will also be faxed directly to your physician. A screen positive result does not mean that your baby has Down syndrome. Rather, it means that you may be at somewhat higher risk for having a baby with Down syndrome. This first trimester test has an 87% detection rate and a 4-5% false positive rate.
The Second Stage:
The second stage involves a blood sample, which is obtained between 15 and 22 weeks of pregnancy. This blood test is the “Quad” screen. This blood sample must be sent to the same laboratory that performed the first trimester assessment. Thus, it is often easiest to have the sample drawn and packaged here at Platte River Perinatal Center. For patients who live out of town, a blood collection kit can be made available to have this second blood test drawn in the referring physician’s office and mailed to our laboratory.
Analysis of this sample is combined with the first trimester results to increase the detection rate for Down syndrome up to 92% with a 5% false positive rate. This second trimester screen also assesses risk for neural tube defects such as spina bifida and for a rare, but devastating, chromosomal anomaly known as Trisomy 18.
These results will be available within 3-5 business days of the blood draw. Results will be called to you and they will be faxed to your physician.
- 92% of pregnancies with Down syndrome can be detected with Early Screening.
- 70% of pregnancies with Down syndrome will have a thickened nuchal translucency.
- 82% of pregnancies with Down syndrome will have a screen positive result in the first trimester.
- 5% of normal pregnancies will have a screen positive result (when the first trimester and second trimester results are combined).
If you are interested in this screening program or if you have questions, you may schedule an appointment or contact us at 303-315-6100.