FMH Classic Reagents

Introduction
Detection and quantification of fetal red blood cells (RBCs) in maternal blood samples is essential for obstetrical management. Measurement of fetal RBCs is critical as the extent of Fetomaternal Hemorrhage (FMH), the transplacental passage of fetal RBCs into the maternal circulation, has consequences for further treatment of mother and child.

Frequency and size of FMH is directly influenced by complications such as abdominal trauma, suspected placental injury or following a caesarean section. In case of antigen incompatibility between mother and child, FMH may result in respiratory problems or anemia, like hemolytic disease of the newborn.

In case of a RhD incompatibility between the fetus and mother, detection (and thus enumeration) of fetal RBCs using an anti-RhD antibody is used to calculate the extent of FMH. The amount of fRBCs is a measure for the prevention of hemolytic disease of the newborn using (prophylactic) anti-D therapy.

Principle of the FMH Classic Reagents

With flow cytometry, the BRAD 3 FITC antibody can be used to accurately quantitate the number of RhD positive cells in a mixture of RhD positive and negative cells. Therefore FMH can be analyzed in a maternal blood sample when a negative woman carries a RhD positive fetus.

For optimal interpretation of the results the kit contains two antibodies BRAD 3 and AEVZ 5.3, both labeled with FITC.

Figure: The figure shows the results of the AEVZ 5.3 FITC and BRAD 3 FITC with RhD positive cells. The blue peak shows the results of AEVZ 5.3 while the red peak shows the results of BRAD 3 FITC.

Conclusion
The FMH Classic Reagents can be used only in cases of Rh incompatibility between mother and child. For all other cases the Fetal Cell Count™ Kit is recommended.