Analysis of renal artery hemodynamics in normal fetuses using the color Doppler method

From analysis of fetal renal artery hemodynamics, we attempted to reveal renal glomerular and tubular function in normal fetuses during pregnancy.

The study included 36 cases of normal fetuses from the 20th to the 40th week of gestation; V(max) (the systolic peak velocity of main renal artery), V(mean) (time averages of trace of peak velocity) blood flow were initially measured between 20 and 24 weeks of gestation and every 4 weeks thereafter. The measurement was performed a total of five times in a longitudinal study. In addition, the blood flow waveform was concurrently examined.

The V(max) was 22.02 +/- 0.50 cm/s at 20-24 weeks of gestation. This standard value (100%) was found to increase for each group as follows: 125.2, 149.1, 156.1, and 181.5%. Furthermore, using 20-24()weeks of gestation as the standard, the V(mean) increased after the 37th week of gestation: 186.7%, respectively. At 20-24 weeks of gestation, the blood flow wave forms consisted of 43.2% type I (only systolic waveforms), and 56.8% type II (both systolic and diastolic waveforms). Type III waveforms (waveforms that extended beyond the diastolic to the next systolic component) were not recognized. In the 33- to 36-week group, 82.6% of the waveforms were type II, and in the 37- to 40-week group, 76.2% of the waveforms were type III.

The V(max) and V(mean) of the renal artery in normal fetuses exhibit a similar rate increase when 20-24 weeks of gestation is compared to 37-40 weeks of gestation. The blood flow waveforms changed as pregnancy progresses; thus, it was inferred that this finding was related to the development of the renal glomerular and renal tubular function.