Objective: Proposal of antenatal Down syndrome screening protocol using integration of first and second trimester results.
Design: Review.
Setting: Antenatal screening centre GENNET, Prague.
Methods: Search of relevant articles, software analysis and pilot implementation.
Results: Screening of Down syndrome (DS) is divided into two phases: at first phase combined DS risk is calculated using pregnancy plasma protein-A (PAPP-A) at 9th-11th gestational week and ultrasound fetal nuchal translucency (NT) at 11th-13th week with risk cut-off 1/100 (about 2 per cent of screened). Positive mothers are counselled immediately after NT measurement: First phase negative mothers continue to second phase where PAPP-A and NT values are integrated with second trimester screening results. Protocol is supported with special software (Obstetrician's Screening Guide-OSG).
Conclusion: At proposed protocol the information on significant first trimester DS risk is not withheld to second trimester and mother can choose early prenatal diagnosis. Expected detection rate is near 90 per cent at 5 per cent false positive rate.