PURPOSE: to analyze the values of Doppler ultrasound for blood flow velocity in the ductus venosus between the 10th and the 14th week of gestation, during the different phases of the cardiac cycle: ventricular systole (wave S), ventricular diastole (wave D), atrial systole (wave a), and angle-independent indexes. METHODS: Doppler was used in this prospective cross-sectional study to examine 276 single pregnancies. Fetus malformations, abnormal nuchal translucency, and women with clinical pathologies were excluded. A Toshiba SSH-140 ultrasound equipment was used. The derivation of Doppler frequency spectra was carried out according to standardized measurement procedures: less than 30ºinsonation angle and 50-70 Hz high-pass filter. The ductus venosus was identified in a median sagittal and ventral plane with the presence of color aliasing due to increase in blood flow velocity. The sample volume (1-2 mm³) was placed immediately at the origin of the ductus venosus. At least three clearly and subsequent waves were available for measurement of standard values. The Levene test and the Bonferroni method were used for statistical analysis. RESULTS: increase in blood flow velocity from 29 cm/s to 37 cm/s (p=0.013) was observed during ventricular systole between the 10th and the 14th week of gestation. Similarly, increase in blood flow velocity was recorded during the ventricular diastole (from 25 cm/s to 32 cm/s, p=0.026). There were no changes in wave a, pulsatility index, and S/a ratio in this period. CONCLUSION: the reference ranges established by this study may serve as the basis for Doppler ultrasound follow-up in a normal patient population. Further studies are required to determine the validity of these parameters and, in particular, for the fetus at risk.
Doppler velocimetry; Ductus venosus; Normal pregnancy
