Reproducibility of fetal ductus venosus blood flow velocity waveforms during first stage of labor.

Objectives: Fetal ductus venosus (DV) blood flow velocity waveforms are significantly altered during contractions in first stage of labor. We have evaluated the reproducibility of these waveforms during and between contractions.
Methods: 90 women between 37th and 41st week of gestation were included in the study. The measurements of the DV were obtained by three different investigators during and between contractions. The pulsatility index for veins (PIV), peak velocity index for veins (PVIV), and fetal heart rate (FHR) were calculated offline. Furthermore, differences in PVIV (PVIVdiff) and PIV (PIVdiff) and a mean of FHR (FHRmean) were calculated. Statistical analysis was used to verify differences in the PIV, PVIV and FHR during and between contractions of each subgroup as well as for the PVIVdiff, PIVdiff and FHRmean between the subgroups.
Results: Investigator 1 examined 49 patients (group 1); investigator 2, 17 patients (group 2) and investigator 3, 24 patients (group 3), respectively. In all subgroups, there was a significant difference for the PVIV and PIV during and between contractions, but not for FHR. There was a correlation between gestational age and PVIVdiff, PIVdiff and FHRmean as well as for maternal age and PVIVdiff and PIVdiff. PVIVdiff and PIVdiff showed significant differences in group 1 compared to groups 2 and 3 (p < 0.001), but not between groups 2 and 3.
Conclusions: Significant differences in the measurements in the three subgroups have been revealed, which may be due to different timing of measurement during the contraction. For future studies further standardization of the measurement protocol should be established.