[Characteristics of the renin-aldosterone system of the fetoplacental complex in fetal erythroblastosis].

Renin activity and aldosterone concentrations have been determined in amniocentesis samples and fetal plasma obtained by intrauterine umbilical vein puncture in 23 women at 25 to 34 weeks' gestation, normal or complicated by hemolytic disease of the fetus. Prior to the intrauterine interventions, Doppler studies of umbilical arterial circulation were done and 1-hour fetal diuresis was measured. Fetal plasma pH and fetoplacental flood volume were determined. Hemolytic disease was shown to increase renin activity and aldosterone concentration in the amniotic fluid and fetal plasma in parallel with reduction in the fetoplacental blood flow and 1-hour fetal diuresis, increase in vascular resistance of fetal placenta and hypoxia. The increase in renin-aldosterone activity of the fetoplacental unit may be a compensatory fetal and chorionic response to hemodynamic and water-mineral balance in the presence of impaired uteroplacental circulation.