Pre- and Neonatal Testing
The Down-Syndrome-Evaluation or "Triple Test" is a blood examination for the identification of the individual risk for fetal chromosomal disorders or a neural tube defect ("open spine"). The main parameters for performing this "Triple Test" are PAPP-A and free beta-hCG for the first trimester screening (completed by the value of the nuchal translucency) or total hCG, unconjugated Estriol (uE3) and AFP (alpha-fetoprotein) for the second trimester screening.
In every pregnancy there is a small risk that the expected child has a chromosomal disorder (e.g. Trisomy 21, Down-Syndrome, formerly known as mongolism). The older the mother is the higher is this risk. Mothers who are 25 years old have a risk of 1:1300, for 30 years old mothers it is 1:900 and for 35 years it is 1:380. Pregnant women who are older than 35 years are offered a withdrawal of liquor amnii, in which the chromosoms of the unborn child are inspected for disorders (amniocentesis).
Performing a blood examination ("Triple test") also can determine the Down-Syndrome-Risk of pregnant women below the age of 35 years. If her risk is similar to the one of a woman at the age of 35 years or if it is even higher then the woman may get a chromosomal analysis using liquor amnii. The result of a Triple test will give a number for the risk of any mother for getting a child with chromosomal anomaly; this value may help her in the decision whether or not she needs the analysis of her liquor amnii. Finally it is only the chromosomal analysis giving definite results about chromosomal abnormalities of the expected child, but unfortunately here exists a spontaneous abort risk of 1-2%.
Neonatal-Testing: Besides the TSH screening the PKU testing is done from every newborn in all developped countries. PKU testing historically has been down by the Guthrie heel prick test. As the sensitivity of this test does not allow the sampling during the first days after birth nowadays the main method is the enzymatic test in almost all countries. In a few technically advanced laboratories the PKU testing already is done by Tandem-MS in routine. The enzymatic method allows to take blood samples from the newborn on day 2 or 3 after the brith, so that this usually can be done during the stay of the mother in the hospital. This improves the logistics significantly, because it is of utmost importance not to miss any newborn for the screening.
