Screening for chromosomal anomalies in the first trimester: a report on the first year of prospective screening for chromosomal anomalies in the first trimester in the Czech Republic.

BACKGROUND The increase in maternal age in recent years has intensified the effort to develop early non-invasive methods for screening for trisomy 21 and other chromosomal abnormalities in prenatal diagnosis. In the first trimester of pregnancy, maternal age, fetal nuchal translucency (NT), maternal levels of free beta- human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) are used as screening markers. We evaluated the introduction of this method of screening for the first time in the Czech Republic. METHODS it is a prospective study for one-year from the beginning of 2004. The risk of trisomy 21(Down's syndrome) was estimated for 686 singleton pregnancies. The specific risk was calculated using the Fetal Medicine Foundation software (FMF) by accredited sonographers. Karyotyping was offered to women with risk >or= 1 in 250. RESULTS In the population screened 18 % of women were aged 35 and more. We found 2 cases of trisomy 21 and 1 case of trisomy 18 (Edward syndrome) resulting in a detection rate of 100 % for trisomy 21 for a 5 % false positive rate (33 of 683). The maternal age of the detected cases was 30, 38 and 42 years. CONCLUSION Introduction of the first trimester screening to our clinic, reduced the number of invasive genetic testing from 18 % to 5 %. 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 university hospital.