['To investigate time intervals of ductus venosus (DV) flow velocity waveforms (FVW) in correlation to fetal heart rate and gestational age and to construct reference ranges for the second and third trimester. Furthermore, we investigate time intervals of FVW through the tricuspid valve.', "Flow velocity waveforms of the DV and through the tricuspid valve were recorded in 135 normal singleton fetuses between 17 and 38 weeks' gestation. Time intervals for systolic (S) and early diastolic (D) peaks were analyzed regarding acceleration time (acc-S for S, acc-D for D) and deceleration time (dec-S for S, dec-D for D), respectively. Similarly, time intervals for both peaks of right ventricular inflow were analyzed regarding acceleration time (acc-E for E-wave, acc-A for A-wave) and deceleration time (dec-E for E-wave, dec-A for A-wave), respectively.", 'In the DV, acc-D and dec-D increased significantly with gestational age. In tricuspid valve, acc-E and acc-A showed a significant increase with gestational age. All parameters except acc-S showed significant negative correlations with fetal heart rate.'] Does reference range for time-related analysis of ductus venosus flow velocity waveforms in singleton pregnancies?