Advances in antenatal screening for Down Syndrome

Antenatal screening for Down Syndrome using maternal age alone is no longer an adequate standard of care. Screening in the early second trimester of p regnancy (between 15 and 20 weeks of pregnancy) using the quadruple test ca n identify 76% of affected pregnancies with a 5% false-positive rate. Scree ning in the first trimester of pregnancy (between 10 and 13 weeks of pregna ncy) is possible using two biochemical markers (PAPP-A and free beta-hCG) t ogether with an ultrasound marker nuchal translucency measurement; using th ese three markers together with maternal age can identify 85% of affected p regnancies, with a 5% false-positive rare. While there is debate over issue s involved in choosing between first and second trimester screening, the mo st effective screening test for Down Syndrome is the integrated test based on the integration of the first trimester and the second trimester markers. This has a 94% detection rate for a 5% false-positive rate. If the false-p ositive rate were set at 1%, the detection rate would be 85%. No other scre ening test for Down Syndrome can detect such a high proportion of affected pregnancies with such a low false-positive rate.