First trimester ultrasound screening for trisomy 21 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 trisomy 21 based on maternal age, fetal nuchal translucency and different combinations of the additional ultrasound parameters: nasal bone (NB), ductus venosus (DV) and tricuspid flow (TR).

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 CRL, NT, NB, DV, and TR were measured. In each case, the risk for trisomy 21 was calculated based on firstly, maternal age (MA), secondly, MA and NT thickness, thirdly, MA, NT and one of the additional markers NB, DV and TR flow, fourthly two of these markers, and finally, all of these additional markers together.

Results: 1,916 pregnancies that met inclusion criteria including 1,823 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 increased the detection rate by 13%, 18% and 23%.

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