The first trimester screening -A Review

The protocols that are most frequently used at present include nuchal translucency measurement by ultrasound and measuring two of the analytes existing in maternal serum. This screening is conducted in weeks 11-14.In the most common screening protocol, NT measurement and serum level of hCG and PAPP-A are combined with each other. By using this protocol, the diagnosis rate of Down syndrome in large scale prospective trial will be 79-87% (with the false positive rate of 5%). In comparison to week 13, if it is reduced, the diagnosis rate of trisomy 18 will be like Down syndrome, and the false positive rate will be only 0.5%.Quad test is the most frequently applied screening test of the second trimester for aneuploidy diagnosis. In general, if women do not start pregnancy cares until the second trimester, or if screening tests of the first trimester are not accessible, Quad test will be conducted as a single test. As it will be discussed later, if Quad test and screening tests of the first trimester are combined, the diagnosis rate of aneuploidy will be higher than the current rate. Keywords: screening, first trimester

screening, first trimester