Objective: Our purpose was to assess the ductus venosus blood flow in trisomy 21 fetuses in the first half of pregnancy and the relation of this blood flow to nuchal thickness.
Study design: The ductus venosus blood flow has been studied in 534 consecutive fetuses between 10 and 18 weeks of gestation who were undergoing prenatal invasive diagnostic procedures. Before the sampling, the velocity during atrial contraction, the pulsatility index for veins, and the ratio of systole-end-systole to diastole were established in the Doppler waveforms and eventually correlated with the fetal karyotype.
Results: Ductus venosus waveforms were successfully obtained in 82% of the pregnancies. Eleven fetuses were found to have trisomy 21; the pulsatility index was abnormally increased (>95th percentile) in 73% (8/11), the ratio of systole-end-systole to diastole was abnormally increased in 45% (5/11), and the velocity during atrial contraction was decreased (<5th percentile) in 27% (3/11).
Conclusions: An abnormally increased ductus venosus pulsatility index was found in a substantial proportion of early trisomy 21 fetuses, and this was apparently independent of nuchal thickening.