The combined test for Down Syndrome in the first pregnancy trimenon in 3316 non-selected pregnant women

The high detection rate (DR) for Down syndrome pregnancies which can be ach ieved by measuring fetal nuchal translucency (NT) early in pregnancy can be improved by combining it with placental hormones (PAPP-A, f beta hCG) and maternal age ("combined test"). In this study we wanted to assess the DR us ing the "combined test" in an unselected population of self-referred pregna nt women at a false positive rate (FPR) of about 5 %. Materials and Methods: NT, PAPP-A, f beta hCG and maternal age were measure d in all women with singleton pregnancies who booked for delivery in our ho spital from 1. 12. 97 to 31.12. 99 and who were between 10 and 13 completed weeks of gestation (crown-rump-length 35 -70 mm). Calculation of the speci fic Down risk was done with the computer program Alpha, Version 5aa (Logica l medical systems, London). Results: A total of 3316 women were tested. Out of 10 Down pregnancies, whi ch occurred in this period of time 9 could be detected with the test. 137 w omen had a positive test result but a non-Down pregnancy (FPR 4.1 %). Conclusions: The combined test is an excellent test for the detection of Do wn syndrome pregnancies in a low-risk population. Discussion: The constant increase in maternal age at the time of delivery can also lead to an improv ed DR if a simple age dependant protocol for Down-detection is used, but on ly at the price of a much higher number of amniocenteses and subsequent abo rtions. The DR for Down syndrome can be increased much more markedly using the "combined test" at a much lower FPR (similar to 5 %).