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Variation in Doppler indices along the length of the cord from the intraabdominal to the placental insertion

Aim. The aim of this study was to assess the feasibility of obtaining umbilical artery Doppler waveforms from the intraabdominal portion (perivesical) of the umbilical arteries and to compare the indices from this site to those from the free loop (FL) of cord placental insertion (PL) and abdominal insertion (AI). Methods. A cross‐sectional study of 71 singleton fetuses of 24–38 weeks of gestation. Umbilical artery Doppler waveforms were obtained from four sites by a single operator and their resulting indices — i.e. resistance index, pulsatility index, and systolic/diastolic ratio — were compared. Waveforms were also obtained from the two perivesical (PVC) arteries and the mean was used for analysis. Statistical analyses were performed using appropriate non‐parametric tests. Results. Doppler waveforms acceptable for inclusion in the study were obtained in 100% of cases from the FL site. There were failures to obtain waveforms that met the inclusion criteria in three (4%) cases at the PL site, three (4.2%) cases at the PVC site, and 12 (16.9%) cases at the AI. The three indices fell progressively with gestation from the PVC to the PL sites. There were no significant differences between the two PVC arteries using non‐parametric test of mean difference for related samples using Wilcoxon signed‐rank test (P>0.05) for all the indices. The relation between the differences at the two ends of the cord was fairly consistent across gestation. Conclusions. Doppler velocimetry at PVC site of the umbilical artery is feasible and easy to perform. The indices obtained at this site are higher than those at the other three sites. There is a need for standardization of the site of sampling in order to ensure consistency for clinical application.