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Updated: Jun 11, 2026

The 4-vessel Sampling Approach to Integrative Studies of Human Placental Physiology In Vivo
Published on: August 2, 2017
Longitudinal reference ranges for umbilical vein blood flow at a free loop of the umbilical cord
K Flo1, T Wilsgaard, G Acharya
1Institute of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.
Objective:
To establish longitudinal reference ranges for the umbilical vein (UV) diameter, velocities and volume blood flow (Q(uv)) at a free loop of the umbilical cord and estimate the UV spatial velocity profile at this site.
Methods:
This was a prospective study of 53 low-risk pregnancies. The UV diameter and blood flow velocities were measured at 4-weekly intervals from 22 + 0 to 39 + 6 weeks of gestation (232 observations) using B-mode ultrasonography and pulsed-wave Doppler. Multilevel regression modeling was used to estimate the reference percentiles.
Results:
The mean UV diameter, velocities and Q(uv) increased with advancing gestation, whereas the Q(uv) normalized for estimated fetal weight decreased. The UV spatial velocity profile coefficient was 0.62.
Conclusion:
We have established reference ranges for serial measurements of Q(uv) at a free loop of the umbilical cord during the second half of pregnancy. The spatial velocity profile of the UV is not completely parabolic at this site.
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