Are there characteristics of the false-negative cases from the first trimester combined screening programme for Down syndrome?

To review if there are any characteristics of false-negative cases from the first trimester combined screening programme for Down syndrome and by that to stimulate new approaches for improvements of the screening performance. We are aware of only two studies based on screening results of false-negative cases. Screening results from false-negative cases show that maternal age is lower, nuchal translucency smaller, pregnancy-associated plasma protein-A level higher, β-human chorionic gonadotropin level lower and crown-rump length bigger than among true positive cases. Around 50% of false-negative cases had a final risk between 1 : 300 and 1 : 1000. There might also be a difference in maternal smoking status, conception method, ethnicity and weight discrepancy between false-negative and true positive cases. New biomarkers and secondary sonographic markers may also characterize false-negative cases, but investigations on these subjects have not been done so far. Finally, we think that the organization of a screening programme in all its details is a very important factor when it comes to optimizing screening performance. Screening parameters of false-negative cases tend toward the values of unaffected pregnancies with lower maternal age, smaller nuchal translucency, higher pregnancy-associated plasma protein-A level, lower β-human chorionic gonadotropin level and bigger crown-rump length than among true positive cases.