Persistent fetal hemoglobin in maternal circulation complicating the diagnosis of fetomaternal hemorrhage.

Abstract

Transplacental hemorrhage can be life threatening to a fetus and has important maternal treatment implications. In contrast, hereditary persistence of fetal hemoglobin is a condition that has little consequence. The Kleihauer-Betke test, which is routinely used to document transplacental hemorrhage, will be positive in either case. We report two cases in which maternal persistence of fetal hemoglobin was unknown and led to the erroneous diagnosis of fetomaternal hemorrhage. These cases highlight both the limitations of the Kleihauer-Betke test and the role of flow cytometry in diagnosing fetomaternal hemorrhage. The use of flow cytometry can clarify Kleihauer-Betke test results when there is known maternal persistence of fetal hemoglobin and can more precisely quantify a fetomaternal hemorrhage for accurate Rh immune globulin dosing.