First-trimester ultrasound screening for trisomy 21 based on maternal age, fetal nuchal translucency, and different methods of ductus venosus assessment.

OBJECTIVE: To examine whether combining the dichotomous assessment of the a-wave and the ductus venosus (DV) pulsatility index for veins (PIV) measurement improves first-trimester screening performance.

METHODS: Retrospective study performed at the University Hospital of Tuebingen based on singleton pregnancies that underwent first-trimester screening including DV flow assessment. In each case, the risk of trisomy 21 was calculated based on maternal age, fetal nuchal translucency, and DV flow either as dichotomous classification of the a-wave, as measurement of the DV PIV, or both.

RESULTS: There were 5280 euploid fetuses and 127 fetuses with trisomy 21. The DV a-wave was reversed in 2.3% and 66.1% in the euploid and trisomy 21 cases, respectively. The DV PIV measurements were above the 95th percentile in 8.3% and 77.2% the euploid and trisomy 21 cases, respectively. For a false positive rate of 3%, the detection rate for trisomy 21 based on maternal age, fetal NT, and DV flow is about 87% irrespective of whether DV is examined as a continuous or dichotomous variable. The combination of both resulted in a small decrease at 3% false positive rate.

CONCLUSION: Assessment of the DV a-wave and the DV PIV result in similar DRs. Combining these two approaches does not appear to improve their individual screening performance. © 2017 John Wiley & Sons, Ltd.