II. Indications

  1. Measures fetal cells in maternal circulation
  2. Used in assessing for Rh Sensitization
    1. Maternal blood Rh negative
    2. Large antepartum bleed

III. Mechanism

  1. Blood Film stained with acid elution
  2. Fetal Hgb more acid resistant
  3. Fetal RBC darkly stained, Maternal RBC "ghosts"

IV. Technique

  1. Count Fetal cells per 50 low power fields
  2. Five cells per 50 (lpf) = 0.5 ml bleed

V. Interpretation

  1. Calculate Maternal Blood Volume (ml) =
    1. (Pre-pregnant weight in kg) x 70 ml/kg x
    2. (1.0 + (0.5 x weeks gestation/36)) -
    3. Estimated Blood loss (ml) at time of test
  2. Calculate Fetal Whole Blood (ml) =
    1. (Fetal Cell Count/Maternal Cell Count) x
    2. Maternal Blood Volume
  3. Rh Immune Globulin (RhoGAM) Dose
    1. Give 300 ug per 30 ml fetal whole blood or 15 ml pRBC

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