Normal values of fetal ductus venosus blood flow waveforms during the first stage of labor

Objective: To present normal values of fetal ductus venosus blood flow waveforms during the first stage of labor during and between contractions. Materials and methods: Seventy-eight women between the 37th and 41st weeks of gestation were included in the study. At distinct stages of cervical dilation, blood flow velocity waveforms of the fetal ductus venosus during and between contractions were visualized in fetuses with a normal non-stress test. The pulsatility index for veins, peak velocity index for veins and fetal heart rate were calculated off-line. The means ± standard deviations (SD) during and between contractions were compared using the Wilcoxon test. Results: Ductus venosus blood flow velocity waveforms were visualized during 331 contractions and 375 episodes of uterine quiescence in 74 of 78 fetuses (95%) during normal labor. The mean ± standard deviation values of pulsatility and peak velocity indices for veins during contractions were 1.66 ± 0.85 (median: 1.56, range: 0.29-4.69) and 1.46 ± 0.65 (median: 1.34, range: 0.26-3.13), respectively. Between contractions the values were 0.48 ± 0.19 (median: 0.46, range: 0.14-1.00) for the pulsatility index and 0.44 ± 0.18 (median: 0.42, range: 0.14-1.00) for the peak velocity index for veins. These differences during and between contractions were highly significant (P-value < 0.0001), whereas the fetal heart rate showed no significant differences. Conclusion: There are significant differences in fetal ductus venosus blood flow waveforms during and between labor contractions. Further studies should evaluate whether these normal values of the fetal ductus venosus are beneficial for risk evaluation in fetuses with an abnormal non-stress test and/or intrauterine growth restriction.