Fetomaternal Bleed, New York

CPT CODE:

USEFUL FOR:

Determining the volume of fetal-to-maternal  hemorrhage for thepurposes of recommending an increased dose of the Rh immuneglobulin (RhIG)

SPECIMEN REQUIRED:

Specimen must arrive within 72 hours (preferably 24 hours) of draw.
Draw blood in a lavender-top (EDTA) tube(s). Do not centrifuge oralliquot. Invert several times to mix blood. Send EDTAwhole blood in original VACUTAINER(S) refrigerated.
Note:  1. Test results may be greatly impacted by improper mixing                and aliquot technique. No aliquoting of draw tube should                be performed.                2. Minimum specimen is 1.0 mL but must be at least 75%                of draw tube maximum volume as the effect of excess                 anticoagulant could be detrimental.                3. Date of delivery or abortion and date of draw are             required on request form for processing.

TRANSPORT TEMPERATURE:

Refrig\Ambient OK\Frozen NO

CLINICAL INFORMATION:

In hemolytic disease of the newborn (HDN), fetal red cells becomecoated with IgG alloantibody of maternal origin, directed againstan antigen on the fetal cells that is of paternal origin and absent onmaternal cells. The IgG-coated cells undergo accelerateddestruction, both before and after birth. The clinical severity of thedisease can vary from intrauterine death to hematological abnormalities detected only if blood from an apparently healthyinfant is subject to serologic testing.
Pregnancy causes immunization when fetal red cells possessinga paternal antigen foreign to the mother enter the maternal circulation, an event described as fetomaternal hemorrhage (FMH).FMH occurs in up to 75% of pregnancies, usually during the third trimester and immediately after delivery. Delivery is the most common immunizing event, but fetal red cells can also enter the mother's circulation after amniocentesis, spontaneous or inducedabortion, chorionic villus sampling, cordocentesis, or rupture of anectopic pregnancy, as well as blunt trauma to the abdomen.(2)
Rh immune globulin (RhIG, anti-D antibody) is given to Rh-negativemothers who are pregnant with an Rh-positive fetus. Anti-D antibodybinds to fetal D-positive red cells, preventing development of the maternal immune response. RhIG can be given either before orafter delivery. The volume of FMH determines the dose of RhIG tobe administered.

CLINICAL INTERPRETATION:

Greater than 15 mL of fetal RBCs (30 mL of fetal whole blood) is consistent with significant fetomaternal hemorrhage.
A recommended dose of RhIG will be reported for all Rh-negativematernal specimens. No dose recommendations will be madefor Rh-positive maternal specimens. One 300 ug dose of RhIGprotects against a FMH of 30 mL of D-positive fetal whole bloodor 15 mL of D-positive fetal red blood cells.

REFERENCE VALUES:

<15 mL of fetal RBCs