Question

PRINCIPLE of the FETAL SCREEN (Rosette Test):

A red cell suspension (EDTA) from the D-negative mother is first incubated with a serum containing anti-D and then washed to remove all unbound antibody, as in the incubation and washing phases of the IAT for weak D. Instead of adding AHG to the washed cells, a weak suspension of enzyme treated D-positive red cells (indicator cells) is added. The cell mixture is centrifuged and examined microscopically for mixed-field agglutination. Since any minor population of D-positive indicator cells added after washing form clumps around the individual fetal cells leading to larger and more readily detected agglutinate. The clumping of the coated cells is referred to as rosetting. In most cases the fetal-maternal hemorrhage is insufficient to cause a positive test. In cases that are positive, a quantitative test (Kleinhauer-Betke stain) is required to determine whether the bleed was sufficient enough to warrant the administration of a larger dose of Rh Immune Globulin to the mother.

PRINCIPLE of the KLEINHAUER-BETKE ACID ELUTION:

The Kleihauer-Betke acid elution is the method used most frequently to quantify the number of fetal cells in the maternal circulation. This method is based on the fact that fetal hemoglobin is resistant to acid elution and adult hemoglobin is not. A blood smear is prepared from a postpartum maternal sample and exposed to an acid buffer. Hemoglobin from adult cells leaches into the buffer and leaves only stroma, whereas the fetal cells retain their hemoglobin. Smears are washed, stained and examined under oil immersion. Adult cells appear as “ghosts” and fetal cells appear pink. Results are reported as the percentage of fetal cells (number of fetal cells divided by the total cells counted). The volume (in milliliters of whole blood) of the fetal-maternal bleed is equal to the percentage of fetal cells multiplied by 50.

Antepartum RhIG:

Postpartum use of Rh immunoprophylaxis has reduced pregnancy-associated immunization to the D-antigen from approximately 13% to 1-2%. The risk is further decreased to 0.1% if RhIG is also given antepartum at 28 weeks gestation. Anti-D from RhIG can remain detectable for as long as 6 months. Antepartum RhIG is given at 28 weeks gestation based on the observation that, of women who develop anti-D during pregnancy, 92% do so at or after 28 weeks. Blood tests before injection should include ABO, Rh and antibody screen and identification if necessary. A D-negative woman who has antibodies other than anti-D is still a candidate for anti-D immunoprophylaxis.

RhIG Dosage Calculation:

mL fetal blood / 30 (mL/dose) = # of doses of RhIG required

Final dose = Required dose + one additional vial

1. When is a mother a candidate for RhoGam?

Answer 1

RhoGAM Ultra-Filtered PLUS [Rho(D) Immune Globulin (Human)] , is a physician endorsed medication given by intramuscular infusion that is utilized to forestall Rh inoculation, a condition where a person with Rh-antagonistic blood creates antibodies after presentation to Rh-positive blood. MICRhoGAM Ultra-Filtered PLUS [Rho(D) Immune Globulin (Human)] (50 μg) is a lower portion of Rho(D) safe globulin that is utilized in certain clinical circumstances.

In the event that the dad or child isn't convincingly demonstrated to be Rh-negative, RhoGAM should be given to a Rh-negative mother in the accompanying clinical circumstances to forestall Rh inoculation:

After conveyance of a Rh-positive child

Routine anticipation of Rh vaccination at 26 to 28 weeks of pregnancy

Maternal or fetal seeping during pregnancy from specific conditions

Genuine or compromised pregnancy misfortune at any stage. MICRhoGAM ought to be utilized in Rh-negative ladies who experience pregnancy misfortune at or as long as 12 weeks of pregnancy. Ectopic (pregnancy in which the treated egg inserts outside the uterus