Ultrasound measurement of umbilical venous flow volume at the intra-abdominal portion in normal fetuses

PURPOSE: Umbilical venous flow volume (UVFV) measured using ultrasound can be used to assess placental circulation in a fetus. UVFV measured at the intra-abdominal portion using half the maximum flow velocity of the umbilical vein (UV) has good reproducibility with low variance. However, reference values in previous reports were based on a small number of cases with a wide reference range. In the present study, we evaluated UVFV standard values measured at the intra-abdominal portion in normal Japanese fetuses. METHODS: Measurements were performed on normal pregnant women during routine ultrasound screening at around 20 or 30 weeks of gestation. The diameter and flow velocity of the UV were measured at the fetal abdomen point between the insertion of the UV and branches of the portal vein. UVFV (ml/min) was calculated as follows: (UV diameter [cm]/2)(2) × maximum velocity [cm/s] × 0.5 × 3.14 × 60). RESULTS: A total of 278 pregnant women were included in the study. UVFV increased with gestational weeks, and UVFV per estimated fetal weight (EFW) slightly decreased with increasing gestational weeks. The 50th (10th–90th) percentiles of UVFV per EFW at 20, 25, and 30 weeks of gestation were 130 (105–165), 123 (94–147), and 104 (80–131) ml/min/kg, respectively. CONCLUSION: New UVFV reference values measured at the intra-abdominal portion of fetuses using large-scale samples were established. Future studies should assess fetuses under pathologic conditions using UVFV reference values.