First trimester ultrasound screening for Down syndrome based on maternal age, fetal nuchal translucency and different combinations of the additional markers nasal bone, tricuspid and ductus venosus flow.

Objective: To examine the performance of screening for Down syndrome based on maternal age, fetal nuchal translucency (NT) and different combinations of the additional ultrasound parameters: nasal bone (NB), tricuspid flow (TF) and ductus venosus (DV).

Methods: Retrospective study at the University of Tuebingen, Germany including women who underwent chorionic villous sampling between 2008 and 2014. Prior to invasive testing, the crown rump length, NT, NB, TF and DV were measured. In each case, the added value of the additional markers NB, TF and DV were compared with screening for trisomy 21 based on maternal age (MA) and NT thickness alone.

Results: A total of 1916 pregnancies met the inclusion criteria, including 1823 fetuses with a normal karyotype and 93 with trisomy 21. Screening based on MA, fetal NT and one, two and three of the additional ultrasound markers resulted in a detection rate of about 80%, 87% and 94%, respectively for a false positive rate of 3%.

Conclusion: Detection rates for trisomy 21 in first trimester ultrasound screening are substantially higher if all three additional markers rather than just one are assessed.