Absence of hyperinsulinemia in isoimmunized fetuses treated with intravascular transfusion.

We serially sampled blood from fetuses of five severely isoimmunized pregnancies at the time of each intrauterine intravascular transfusion and at birth. We were unable to demonstrate either an elevation in the plasma insulin/glucose ratio or a relationship between the insulin/glucose ratio and hemoglobin concentration at any time period. Plasma total glutathione concentration, however, decreased dramatically from the initial to the second transfusion (323 +/- 114 to 43 +/- 9 ng/ml; t = -5.06, p less than 0.01). We speculate that intrauterine transfusion may modify or prevent the previously reported fetal pancreatic beta-cell hyperplasia and hyperinsulinemia associated with isoimmunization by decreasing red blood cell hemolysis and thereby circulating glutathione.