Reference values for ductus venosus Doppler flow measurements at 10-14 weeks of gestation

Objectives: To calculate reference ranges for ductus venosus Doppler measurements obtained transabdominally at 10-14 weeks of gestation. Design: Two hundred and one normal fetuses with a crown-rump length (CRL) ranging from 38 to 88 mm were examined in a cross-sectional study. The pulsatility index for veins (PIV), peak velocity during ventricular systole (S-wave), lowest forward velocity during atrial contraction (A-wave) and time-averaged maximum velocity (TAMXV) were recorded from the ductus venosus. Flow velocity waveforms were also classified as normal or abnormal according to the presence (normal) or absence or reversal (abnormal) of frequencies during atrial contraction. Results: Three of 201 fetuses showed an abnormal flow pattern (1.5%; 95% exact confidence interval, 0.3-4.3%). In the 198 fetuses with a normal flow pattern, the mean PIV ranged from 1.07 at a CRL of 38 mm to 1.00 at a CRL of 88 mm (r = -0.093; P = 0.19). A significant increase in mean blood flow velocity with increasing CRL was noted for the S-wave (27.0 cm/s to 33.6 cm/s;r = 0.17; P = 0.02), the A-wave (5.9 cm/s to 7.8 cm/s;r = 0.14; P = 0.04) and the TAMXV (19.4 cm/s to 25.3 cm/s; r = 0.19; P <0.01). Crown-rump length-specific reference ranges for each parameter were calculated using the method of scaled absolute residuals. Conclusions: Abnormal ductus venosus flow patterns could be observed in normal fetuses, even if they ocurred with a low prevalence. Reference values for Doppler measurements were established in fetuses with normal patterns of flow.