From the Research
A Kleihauer-Betke test is indicated at 28 weeks of gestation for Rh-negative women who are not sensitized. This test is performed to detect fetal-maternal hemorrhage, which can lead to maternal alloimmunization against the Rh antigen if the fetus is Rh-positive. The timing at 28 weeks coincides with the administration of Rh immune globulin (RhIG) prophylaxis, which prevents the mother from developing antibodies against fetal red blood cells. The Kleihauer-Betke test quantifies the amount of fetal blood that has entered the maternal circulation, allowing for appropriate dosing of RhIG. The standard dose is 300 mcg for most pregnancies, but additional doses may be needed if significant fetal-maternal hemorrhage is detected, as seen in a case of massive fetomaternal hemorrhage where the patient received 4800 µg of Rho(D) immune globulin 1. The test should also be performed after potentially sensitizing events such as trauma, amniocentesis, or placental abruption, regardless of gestational age, as supported by a study that found Kleihauer-Betke testing accurately predicts the risk of preterm labor after maternal trauma 2. Early detection and appropriate management of fetal-maternal hemorrhage is crucial to prevent hemolytic disease of the fetus and newborn in subsequent pregnancies.
Some studies have suggested that the Kleihauer-Betke test may not be necessary in certain situations, such as after an uneventful external cephalic version, where the risk of detectable fetomaternal hemorrhage is low 3. However, the most recent and highest quality study available does not provide a clear alternative to the standard practice of performing the Kleihauer-Betke test at 28 weeks of gestation for Rh-negative women who are not sensitized.
Key points to consider:
- The Kleihauer-Betke test is used to detect fetal-maternal hemorrhage and quantify the amount of fetal blood in the maternal circulation.
- The test is typically performed at 28 weeks of gestation for Rh-negative women who are not sensitized.
- The standard dose of RhIG is 300 mcg, but additional doses may be needed if significant fetal-maternal hemorrhage is detected.
- The test should also be performed after potentially sensitizing events, regardless of gestational age.
- Early detection and appropriate management of fetal-maternal hemorrhage is crucial to prevent hemolytic disease of the fetus and newborn in subsequent pregnancies.