Binary Test
To check for Down's syndrome, we do a double screening test early in pregnancy, between 11 and 14 weeks. The dual test involves measuring two hormones in the blood, PAPP-A and free b-hCG. If we observe an abnormal condition early in the pregnancy with the dual test, we may consider further diagnostic testing options (chorionic villus sampling, early or late amniocentesis).
The dual test alone can detect 85-90% of babies with Down syndrome.
Nuchal Translucency:
Nuchal translucency measurement performed ultrasonographically between 11 weeks 1 day and 13 weeks 6 days of pregnancy can detect 60% of babies with Down syndrome and some other anomalies, especially heart anomalies. When we evaluate the nuchal translucency measurement and dual test results together, we can detect 50-55% of babies with Down syndrome.
The most important factor here is that the physicians who perform nuchal translucency should have undergone a certain training and have sufficient experience.
Triple and Quadruple Test
The quadruple test is a risk calculation based on measurements of alphafetoprotein (AFP), b -hCG, unconjugated estradiol and inhibin in maternal blood. With the triple and quadruple test, unlike the double test, we can also monitor the risk of neural tube defects.
It is important to remember the following about screening tests. Double, triple and quadruple screening tests do not give a hundred percent result about the health of the baby. These are community screening tests and statistically tell us how much risk there is. Likewise, they do not necessarily indicate that the baby has a disease.