II. Indications
- Measures fetal cells in maternal circulation
- Used in assessing for Rh Sensitization
- Maternal blood Rh Negative
- Large antepartum bleed
III. Mechanism
- Blood Film stained with acid elution
- Fetal Hgb more acid resistant
- Fetal RBC darkly stained, Maternal RBC "ghosts"
IV. Technique
- Count Fetal cells per 50 low power fields
- Five cells per 50 (lpf) = 0.5 ml bleed
V. Interpretation
- Calculate Maternal Blood Volume (ml) =
- (Pre-pregnant weight in kg) x 70 ml/kg x
- (1.0 + (0.5 x weeks gestation/36)) -
- Estimated Blood loss (ml) at time of test
- Calculate Fetal Whole Blood (ml) =
- (Fetal Cell Count/Maternal Cell Count) x
- Maternal Blood Volume
-
Rh Immune Globulin (RhoGAM) Dose
- Give 300 ug per 30 ml fetal whole blood or 15 ml pRBC