Implementation of One-Stop-Clinic for Risk Assessment of chromosomal abnormalities in the first trimester, evaluating the effectiveness and making it part of our daily practice.

Objectives: Implementation and introducing of first trimester screening using nuchal translucency (NT), nasal bone (NB), maternal serum pregnancy associated plasma protein-A and free beta-human chorionic gonadotropin (PAPP-A and fbeta-hCG) as a new method of screening for Down's Syndrome in a One-Stop-Clinic for Assessment of Risk for chromosomal abnormalities in the Czech Republic. To prove its effectiveness and make it part of our daily practice. Modify and/or withdraw the existing current practice.

Methods: Prospective study of 5010 singleton pregnancies who attended our clinic for prenatal screening for chromosomal and congenital abnormalities between 11-13+6 weeks gestation from January 2005 to December 2007. Pregnancies were followed up to ascertain live birth of Down syndrome babies.

Conclusion: The uptake was 100% for screening and around 95% for invasive testing in the screen positive group. All expected trisomies 21 were detected along with many other aneuploidies for false positive rate of 4.4%. The study demonstrated the feasibility and efficacy of introducing OSCAR for chromosomal abnormalities in a University Hospital setting. The introduction of an examination of nasal bone reduced our false positive results and increased our sensitivity. Women who participated in our screening strategy were no longer advised to undergo the triple test.