Objectives: In recent years has been intensified an effort to develop early more exact non-invasive methods for prenatal diagnosis. We report our experience to screen trisomy 21 and other chromosomal abnormalities in the first trimester in so-called OSCAR (One-Stop Clinic for Assessment of Fetal Risk). Design and setting: It is a retrospective study held at the Department of Medical Genetic and Fetal Medicine, Teaching Hospital, Olomouc. Methods: A group of 2110 pregnant women has been screened by maternal age as a background risk, fetal nuchal translucency, nasal bone as ultrasound markers as well as maternal serum level of free β-subunit human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein-A (PAPP-A) as a biochemical markers between 11 – 13+6 weeks of pregnancy from January 2004 to December 2005. The Fetal Medicine Foundation Guidelines and software were the methods and tools used for screening. Karyotyping by chorionic villous sampling or amniocentesis was offered to women with risks ≥ 1 in 300. Results: We reported 100% sensitivity for this method for a 4, 6% false positive. There was detected 21 chromosomal abnormalities in which 10 were trisomy 21. This is the first result to be published for this screening method in the Czech Republic. Conclusion: In our experience first trimester screening for trisomy 21 and other aneuploidies has a high sensitivity with a low false positive rate and can be delivered in an efficient manner in a one-stop multidisciplinary clinic.

        Key words: first trimester screening, OSCAR, nuchal translucency, PAPPA, free β-hCG