Kleihauer-Betke Testing for Fetal-Maternal Hemorrhage
Massive fetal-maternal hemorrhage (FMH) may be the cause in up to 1 in every 50 stillbirths. No historical or clinical features reliably identify those in whom it may be the cause of an intrauterine death. So, unless all stillbirths are tested, a large proportion of FMH will remain undetected. Cost is modest. The information gained is important because recurrence risks may be less than for unexplained stillbirth.
- Stillbirth assessment should, in all instances, incorporate testing of maternal blood for evidence of massive fetal-maternal hemorrhage.
- Blood drawing can be done pre- or postpartum at the convenience of the care provider and the mother; only if cesarean section is anticipated is it important to draw the sample prior to delivery.
- Standard Kleihauer-Betke testing in any experienced laboratory is sufficient. (In this test, by acid elution the mother's red blood cells become very pale while fetal cells, which contain a different form of hemoglobin, remain stained. Simple comparative counts allow an estimate of whether a significant fetal-maternal transfusion occurred.)
- In those with positive tests (20% or more of estimated fetal blood volume lost), follow up testing (at a postpartum check) should be done to rule the possibility of a false positive because of a process, such as e.g. sickle cell trait, in the mother which causes persistent elevation of fetal hemoglobin.
For a complete discussion of the justification for testing for FMH and methods of estimating the percentage of fetal blood volume lost, see WiSSPers, volume 1, number 1.