Successive development of different methods to screen down syndrome (DS) have had unexpected effects, leading to an inflation in the number of karyotypes ordered and the number of induced abortions. In our district (Yvelines, France), DS screening leads to perform 16% karyotypes rate. Rapid progress in biology and ultrasonography has enabled us to correct this overprescription by conducting an early screening program using a combination of ultrasound graphic and new biochemical markers (Pregnancy-associated plasma protein A and the free fraction of ss-hCG) which allow an overall evaluation of risk. This method has high sensitivity (85%) and leads to a false positive rate karyotypes in about 5% of pregnancies. The purpose of the study conducted between January 1, 2001 and December 31, 2002 in the Yvelines was to confirm the validity of this method and determine its reproducibility in routine practice. Five partners contributed to the study: the Regional delegation for clinical research of the Paris-public assistance hospitals (AP-HP), the district health insurance fund (CPAM 78), the Yvelines maternity network which includes all ten maternity wards in the district, and the Echo 78 association which includes all ultrasoundgraphists working in the district who accepted to participate as investigators, as well as five biology laboratories where DS screening was performed.