Arginine vasopressin and acute, intravascular volume expansion in the human fetus.

There is presently no information concerning the ontogeny and control of arginine vasopressin (AVP) in the human fetus. AVP was measured in 22 nonanemic control fetuses and 7 fetuses with hemolytic anemia undergoing 13 intravascular transfusions. Each transfused fetus received pancuronium (0.3 mg/kg) and furosemide (2 mg/kg). Compared to the control group of nonanemic fetuses with hemolytic disease, AVP was significantly lower in the anemic fetus prior to transfusion (2.6 +/- 0.4 microU/ml versus 10.4 +/- 4.1 microU/ml, p less than 0.05). This suggests that hemolytic anemia is associated with a relative increase in fetal intravascular volume. Intravascular transfusion was associated with a significant increase in AVP (p less than 0.05). These findings could not be explained by changes in either blood pressure, plasma osmolality, or fetal oxygenation.