Ductus venosus Doppler assessment: do the results differ between the sagittal and the transverse approach?

Objective: To compare the ductus venosus (DV) pulsatility index for veins (PIV) obtained in a mid-sagittal plane with that obtained in an oblique transverse plane of the fetal abdomen. Methods: Prospective observational study in singleton uncomplicated pregnancies undergoing an ultrasound examination between 24 and 34 weeks of gestation. Pregnancies complicated by fetal anomalies, fetal growth restriction, or oligohydramnios were excluded. Two consecutive recordings of DV Doppler waveform were obtained in each woman: one in a mid-sagittal plane, and the other in an oblique transverse plane of the fetal abdomen. The peak velocity during ventricular systole (S-wave) and diastole (D-wave), the velocity during atrial contraction (a-wave), and the time-averaged maximum velocity (TAmax) were measured, and the PIV was calculated. The paired t-test was used to compare results obtained with the two approaches. A change of the DV-PIV of 0.10 or more was considered clinically relevant. Results: The DV waveform was successfully obtained in 53 women (mean gestational age 28.5 weeks). The mean DV-PIV was 0.57 (±0.16 SD) in the sagittal plane and 0.54 (±0.16 SD) in the transverse plane. The mean difference (0.03) was statistically significant (p = .04), but not clinically relevant. The sagittal S-, D-, and a-wave velocities and TAmax were significantly higher in the sagittal plane compared to the transverse plane, with an increase of 12, 8, 8, and 10%, respectively (p<0.05). Conclusions: The difference in the DV-PIV obtained in a mid-sagittal plane compared to a transverse plane of the fetal abdomen is small and not clinically significant. The higher DV flow velocities observed in the sagittal plane are likely the result of a better alignment with the vessel obtained using this plane. These findings have implications for clinical practice and for research.