Early pregnancy screening for fetal aneuploidy with serum markers and nuchal translucency

Abstract

We determined the aneuploidy detection rate achievable by early pregnancy screening with pregnancy associated plasma protein (PAPP)‐A, free β human chorionic gonadotrophin (hCG) and ultrasound nuchal translucency (NT) measurement. Women having prenatal diagnosis were scanned, and a blood sample was taken and stored. Stored samples were tested and a total of 37 were found to have Down syndrome, 8 to have Edwards syndrome and 255 were controls. Results were expressed in multiples of the gestation‐specific median (MOM) value in the controls after regression and, for the serum markers, maternal weight adjustment. In Down syndrome the medians were for PAPP‐A 0.63 MOM (95 per cent confidence interval (CI) 0.45–0.87); free β‐hCG 1.88 MOM (1.33–2.66); and NT 2.34 MOM (1.70–3.22). Using these parameters the expected detection rate for a 5 per cent false‐positive rate for different marker combinations were: 55.3 per cent for PAPP‐A and free β‐hCG; 68.4 per cent for NT alone; and 84.6 per cent for PAPP‐A, free β‐hCG and NT. The median values for Edwards syndrome were: 0.17 MOM for PAPP‐A; 0.18 MOM for free β‐hCG; and 2.64 MOM for NT. Early pregnancy screening with the combined measurement of maternal serum PAPP‐A and free β‐hCG and fetal nuchal translucency could achieve a high Down syndrome detection rate. Copyright © 1999 John Wiley & Sons, Ltd.