Fetal umbilical velocimetry using continuous-wave and pulsed-wave Doppler ultrasound in high-risk pregnancies: a comparison of systolic to diastolic ratios.

Systolic to diastolic (S/D) ratios of umbilical velocimetry using either continuous-wave or pulsed-wave Doppler ultrasound have been used to assess downstream placental resistance. The purpose of this study was to compare the S/D ratios obtained by both types of instrumentation to determine whether there are significant differences between measurement values. Umbilical velocimetry was performed on 200 high-risk pregnancies in the third trimester using the Angioscan III to obtain continuous-wave velocimetry and the General Electric RT3600 to obtain pulsed-wave velocimetry. Systolic to diastolic ratios were considered abnormally high if they were greater than 3. One hundred sixty-five patients had normal S/D ratios and 35 patients had elevated ratios on both continuous-wave and pulsed-wave ultrasound. There was no significant difference in the mean S/D ratios obtained by either method for the entire population (continuous-wave S/D 2.81 +/- 1.79, pulsed-wave S/D 2.71 +/- 1.83, R = 0.98), the normal group (continuous-wave S/D 1.96 +/- 0.41, pulsed-wave S/D 1.95 +/- 0.40, R = 0.91), and the abnormal group (continuous-wave S/D 6.23 +/- 1.58, pulsed-wave S/D 6.35 +/- 1.52, R = 0.94). Least-square regression was performed to model the relationships between pulsed wave and continuous wave, with both used as dependent variables. The slopes and intercept for the normal and abnormal groups were evaluated and were significantly different (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)