Rational use of Doppler ultrasound in perinatal medicine.

Doppler ultrasound velocimetry of uteroplacental, umbilical and fetal vessels provides the clinician with important information on the hemodynamics of respective vascular area. Gestational age-related reference values have been established for maternal uterine and arcuate artery, umbilical artery, fetal descending aorta, and fetal cerebral, renal and femoral arteries. Recently, velocimetry of the fetal central venous system gained increasing attention. In growth-retarded fetuses and fetuses developing intrauterine distress, the umbilical artery blood velocity waveform changes in a typical way: the diastolic velocity of the waveform decreases and eventually disappears. The absent or reverse end-diastolic flow (ARED flow) is associated with high risk of intrauterine demise and adverse perinatal outcome. Applied as a screening test in an unselected pregnant population, umbilical artery velocimetry has not been found useful. In a preselected population of high-risk pregnancies, especially pregnancies with SGA fetuses, the method has a high predictive value with regard to diagnosing fetal compromise and can be used for monitoring fetal health. A meta-analysis of randomized clinical trials showed that including Doppler velocimetry in the management of high-risk pregnancies lowers the perinatal mortality. Follow-up studies, few published so far, showed an association between the abnormal intrauterine umbilical and/or fetal blood flow and subsequent postnatal neurodevelopmental impairment. Doppler velocimetry of umbilical artery applied in management of high risk pregnancies improves the perinatal outcome and can thus be considered a clinical method of fetal surveillance.