Objective: Umbilical vein blood flow has been previously determined in the ovine fetus by the steady state diffusion technique which requires fetal catheters. The aim of our study was to determine whether umbilical vein blood flow obtained by doppler velocimetry is similar to that obtained by ethanol (EtOH) and tritiated water (3H2O) steady state techniques. Study Design: Seven ewes at 125-133 days' gestation underwent an ultrasound and doppler examination. In a supine position, pulsed doppler velocimetry was used to obtain three time average mean velocities (TAM) of the UV and real time ultrasound used to obtain the diameter of the UV at the same location as the TAM. Volume flow (VF) was determined by the following formula: VF (ml/min) =πr2 × TAM(cm/s) × 60sec × 2. These results were compared to historical data from 34 ewes at the same gestation and under similar conditions in which UV flows were obtained by steady state techniques using EtOH or3 H2O. These UV flows represent VF at the level of the confluence of the two umbilical veins just beneath the umbilicus of the fetus where sampling catheters were placed. Gestational age, fetal weights, and VF between doppler and steady state technique groups were analyzed for variance and statistical differences using the f-test and unpaired t-tests, respectively. Data are presented as mean ± S.E.. Results: Gestational age and fetal weights were not different between doppler (129.6± 2.8 days; 2.75 ± 0.26 kg) and steady state groups (131.6± 4.1 days; 2.94 ± 0.68). Variability between the groups were similar (f-test; 0.138). No technique groups (205.7±38.5 ml/kg min) for VF (p=0.881). Conclusion: VF as determined by significant differences were detected between the doppler (210.8±18.8 ml/kg min) and dilutional doppler velocimetry is similar to that obtained by steady state dilutional techniques. Doppler velocimetry can be used to assess gestational age-related changes in UV volume flow in a non-invasive fashion.
