Volumetric flow in the umbilical artery: Normative data

Abstract

Objective: Provide normative data for the volumetric blood flow (cc/min and cc/min/kg) in the umbilical artery.

Methods: Flow was determined from an umbilical artery in 252 normal obstetrical patients from 18–40 weeks' gestation utilizing pulsed Doppler and color flow Doppler with an angle of insonation of 30–60°. Simultaneous velocimetry studies (S/D ratio, resistance and pulsatility indices), fetal biometry, and an anatomic survey were obtained to further define the normal population.

Results: There was a steady increase in the flow (cc/min) in the umbilical artery as pregnancy progressed. Flow/kg showed a steady decline as fetal weight increased. Umbilical artery diameter increased until reaching a plateau at 32–34 weeks. Velocimetric results were consistent with known data.

Conclusions: Volumetric blood flow in the umbilical artery can be determined with relative ease and normative data from 18–40 weeks is presented for the first time.

Key Words:

• umbilical artery
• volumetric flow
• Doppler velocimetry