Background: Fetal erythrocytes cross the placenta during gestation, but invasive prenatal procedures might develop into fetomaternal hemorrhage (FMH). We examine whether flow cytometry immunophenotyping might be useful for measuring the volume of FMH after such procedures.
Methods: Fetal erythrocytes (%) were determined in 153 pregnant women after amniocentesis (129) and chorionic villous sampling (24) using a monoclonal antibody against fetal hemoglobin. Fetal erythrocytes were identified for their high expression of fetal hemoglobin (HbF(++) ). Blood samples from two control groups, 53 healthy males and 21 pregnant women not submitted to invasive tests, were used to establish normal values of circulating HbF(++) erythrocytes in adults.
Results: The highest percentage of HbF(++) erythrocytes in the control groups was 0.015%. The rate of HbF(++) erythrocytes in samples after invasive tests ranged between <0.01% and 0.15%. Seventy-three women (47%) had ≤0.015% HbF(++) erythrocytes, and this rate was higher in 80. Nine women presented >1 ml of FMH (volume of packed cells corresponding to 0.054-0.15% HbF(++) erythrocytes), but only two had sonographic evidence of bleeding.
Conclusions: Most women in our series had a very low volume of FMH after the invasive tests. Acute bleeding should be thoroughly investigated in women with either more than 1 ml of packed cells or more than 0.05% of HbF(++) erythrocytes. Intermediate values between >0.015% and <0.05%, should be carefully considered depending on the week of gestation. Data obtained before 15 weeks might reflect previous cell trafficking between fetus and mother instead of acute hemorrhage.
Copyright © 2010 International Clinical Cytometry Society.