REFERENCE VALUES FOR DOPPLER VELOCIMETRIC INDEXES FROM THE FETAL AND PLACENTAL ENDS OF THE UMBILICAL ARTERY DURING NORMAL-PREGNANCY

A range-gated Doppler ultrasound system combined with a real-time imag ing system was used to determine arterial blood velocity values from t he fetal and placental ends of the umbilical cord in 269 normal pregna ncies between 17 and 40 weeks, menstrual age. The systolic-diastolic r atio (S/D), pulsatility index (PI), and resistance index (RI) were hig her at the fetal end compared to the placental end of the cord. The in dividual differences in these Doppler indices, obtained between the fe tal and placental recording sites, were inversely related to menstrual age: S/D: r = -0.38, p < 0.001; PI: r = -0.25, p < 0.001; and RI: r = -0.15, p < 0.01. After normalization for the angle of insonation, the peak systolic velocity was higher and the end-diastolic velocity was lower at the fetal than at the placental end of the cord. It is conclu ded that routine recordings for Doppler velocimetric indices should ta ke into account the recording site on the umbilical cord in order to r educe methodological sources of variance, especially during midgestati on. Furthermore, the data presented here in the form of the median and percentile values are proposed as normal reference values to facilita te this procedure.