[Obstetric cw-Doppler--results of a study of normal values. Effect of different variables on results]

Using a 4 MHz continuous wave Doppler device reference values for resistance index (RI) and pulsatility index (PI) of uterine and arcuate arteries as well as umbilical artery were established based on 510 patients with uneventful pregnancies and deliveries. Percentiles are more suitable localisation gauge than are standard deviations. Neither RI nor PI of maternal arteries proved to be dependent on gestational age in the observation period. If the heart rate are in physiological ranges no clinically relevant effect on the results were observed in either the maternal of the foetal copartment. By contrast umbilical artery shows a definite linear relation between the indices measured and gestational age. A significant effect of placental site on the measurement was found in both, uterine and arcurate arteries, but only the differences found in arcuates were of clinical value. An increase of diastolic notching was observed in both, uterine and arcuate arteries during pregnancy. Mostly only one vessel showed diastolic notching when observed in normal pregnancy. With a lateralized placenta the condition was more probable on the contralateral site.