- Last Update On : 2013-01-22
61 Fetal maternal hemorrhages can occur during the first and second trimesters or at term during separation of the placenta. Clinically, it is often important to know the source and extent of bleeding. Fetal RBCs can be quantitated using the Kleihauer-Betke technique. The quantitation of fetal RBCs is useful in the following clinical situations:
- To determine if a vaginal bleed during pregnancy is from mother or fetus.
- To determine the source of blood in amniotic fluid.
- To calculate the dose of Rh immune globulin needed to prevent Rh sensitization in an Rh negative women with a positive fetal blood screen postpartum.
Results are reported as the percent of fetal RBCs seen. The sensitivity of the method is approximately 0.1 mL of fetal blood in the maternal circulation. This corresponds to about 1 fetal cell per 50, 000 maternal cells. The Kleihauer-Betke stain may occasionally underestimate the number of fetal RBCs present due to the fact that the fetus begins to synthesize hemoglobin A in the last trimester of pregnancy. Fetal cells, which had completed the switch to adult hemoglobin, would be counted as adult cells.
False positive reactions may occur when maternal RBCs have increased levels of hemoglobin F such as occurs in various hemoglobinopathies including hereditary persistence of fetal hemoglobin, thalassemias, and sickle cell anemia.
Reference range is no fetal RBCs present.
Specimen requirement is one 7 mL lavender top (EDTA) tube of blood or one mL of amniotic fluid or vaginal blood.