Guidelines for the use of Rh (D) immunoglobulin (Anti-D)

In pregnant women with Rh (D) negative blood group, and no pre-existing Anti-D antibodies

For best practice the 2003 NHMRC Guidelines (2) recommend:

• Rh (D) Immunoglobulin should be administered as soon as possible after the sensitising event, but always within 72 hrs for successful immunoprophylaxis.

• If Rh (D) Immunoglobulin has not been administered within 72 hrs, a dose offered within up to 9-10 days may provide protection.

• Rh (D) Immunoglobulin should not be given to women with preformed anti-D antibodies, except where the preformed anti-D is due to the antenatal administration of Rh (D) Immunoglobulin.

• Rh (D) Immunoglobulin 100 IU is sufficient to protect against a Fetomaternal Haemorrhage (FMH) of 1.0 mL of fetal red cells (2.0 mL whole blood).

• Quantify the magnitude of the FMH following a sensitising event (including delivery) to ensure an adequate dose of Rh (D) Immunoglobulin is offered as more than one dose may be required.

• Tests to assess the volume of FMH include but are not limited to the Kleihauer-Betke acid elution test and flow cytometry.

• The majority of fetal bleeds are less than 5 mL of red blood cells.

• In about 50% of cases, FMH is less than 0.05 mL
• In about 5% of cases, FMH is greater than 0.5 mL
• In about 3% of cases, FMH is greater than 1 mL
• In up to 0.6% of cases, FMH is 30 mL or greater

For each sensitising event*, administer Rh (D) Immunoglobulin as indicated below(1).

* Sensitising events include (2):
normal delivery, ectopic pregnancy, miscarriage, termination of pregnancy, genetic studies such as chorionic villus sampling, amniocentesis, cordocentesis, abdominal trauma considered sufficient to cause fetomaternal haemorrhage, external cephalic version and antepartum haemorrhage

The batch number of every vial of human immunoglobulin administered must be recorded in the patient's medical history and in accordance with other legal statutory requirements.

**In some circumstances, access to an intravenous preparation may be warranted. A quantity of intravenous Rh (D) immunoglobulin will be available for this purpose. Contact ARCBS in your capital city for more information.

• Approximately 17% of pregnant caucasian women will be Rh (D) negative, and their babies (if Rh (D) positive) may be at risk of developing Haemolytic Disease of the Newborn (HDN) due to Rh (D) incompatibility (2).

• Antibody formation occurs during pregnancy in 1.5% of Rh (D) negative women carrying a Rh (D) positive infant, despite use of
postnatal prophylaxis (2) .

• The rate of antibody formation can be reduced to 0.2% or less by the administration of Rh (D) Immunoglobulin during pregnancy,
at 28 weeks and 34 weeks (antenatal prophylaxis), as well as after delivery (2).


References
1. Communication from Professor Richard Smallwood, Chief Medical Officer,
Commonwealth of Australia (November 2005)
2. NHMRC Guidelines on the prophylactic use of Rh (D) Immunoglobulin (Anti-D)
in obstetrics 2003; www.nhmrc.health.gov.au

Please review the Approved Product Information for Rh (D) Immunoglobulin before prescribing.