Reference ranges for ductus venosus velocity ratios in pregnancies with normal outcomes.

OBJECTIVES

The purpose of this study was to establish reference ranges for ductus venosus velocity ratios.

METHODS

Singleton pregnancies from 11 to 38 weeks with exactly established gestational ages (GAs) were recruited for the study. Pregnancies with fetal anomalies, growth abnormalities, maternal medical complications, stillbirth, birth weight below the 10th or above the 90th percentile, and neonatal anomalies were excluded. The ductus venosus pulsatility index for veins (PIV) and velocity ratios (S/v, S/D, v/D, S/a, v/a, and D/a, where S indicates ventricular systole [s-wave], v, ventricular end-systolic relaxation [v-descent], D, passive diastolic ventricular filling [D-wave], and a, active ventricular filling during atrial systole [a-wave]) were calculated. Separate regression models were fitted to estimate the mean and standard deviation at each GA for each ratio.

RESULTS

A total of 902 velocity wave ratios and ductus venosus PIVs were used for reference ranges. The S/v, S/D, and v/D ratios were not changed with GA (P > .05 for all). The PIV and S/a, v/a, and D/a ratios were reduced with GA (P < .0001 for all). Significant reductions in the means and standard deviations of the PIV and S/a, v/a, and D/a ratios were observed between 17 and 18 weeks' gestation. Therefore, nomograms were separately created between 11 and 17 weeks and 18 and 38 weeks.

CONCLUSIONS

We created reference ranges for ductus venosus velocity ratios between 11 and 38 weeks' gestation in normal pregnancies. These reference ranges may prove beneficial for evaluation of fetal conditions that are associated with cardiovascular abnormalities.