Increased levels of carboxyhemoglobin and serum iron as an indicator of increased red cell turnover in preeclampsia.

Patients with severe preeclampsia are reported to have microangiopathic hemolytic anemia. This study demonstrates that increased red cell turnover with heme catabolism is also common in mild preeclampsia. Heme catabolism results in equimolar production of carboxyhemoglobin, iron, and bilirubin. A concomitant rise in these constituents of venous blood would support this hypothesis. Patients with antepartum preeclampsia had mean carboxyhemoglobin concentrations (2.72% total hemoglobin) greater than those of control patients (0.65%) (p less than 0.001) and serum iron concentrations (98.5 micrograms/dl) greater than those of control patients (66.1 micrograms/dl) (p less than 0.01). Bilirubin concentrations were not different. Post partum, carboxyhemoglobin and iron concentrations returned toward normal (1.38% and 50.2 micrograms/dl, respectively). Disparity in the magnitude of increase of heme catabolites produced in equimolar proportion is explained by differences in the kinetics of clearance. The data are most consistent with increased destruction of maternal red cells, even in mild preeclampsia. Potential implications of elevated carboxyhemoglobin on maternal and fetal oxygenation are discussed.