[Evaluation of fetal renal arterial blood flow waveforms with pulsed Doppler flowmetry and the correlation to estimated fetal body weight, fetal urine production rate and amniotic fluid volume].

Fetal renal arterial blood flow waveforms in 69 fetuses at 28 to 41 weeks of gestation were evaluated by means of pulsed doppler flowmetry. The pulsatility index (PI) in non-retarded fetuses gradually decreased as the gestational age advanced. A negative correlation was found between the PI in non-retarded fetuses and the weeks of gestation (r = -0.676, p less than 0.01). PI of the renal artery was higher in IUGR than in non-retarded fetuses, and no negative correlation was found between the PI in IUGR and gestational age (r = -0.337). The PI in all fetuses including IUGR was negatively well-correlated to estimated fetal body weight (r = -0.633, p less than 0.01). These results showed that the PI of the renal artery has a negative correlation with fetal body weight but not with aging of the fetus. The rate of fetal urine production in 19 cases and the diameter of the amniotic pocket in 44 cases at 36 to 40 weeks of gestation were next examined. The PI of the fetal renal artery also showed a negative correlation to the urine production rate (r = -0.544, p less than 0.01) and the diameter of the amniotic pocket (r = -0.517, p less than 0.01). The results suggested that an increase in the impedance of the fetal renal artery causes a decrease in urine production. These observations indicated that the assessment of renal blood flow waveforms may be useful in evaluating the development and well-being of the fetus.