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Rh D immunoglobulin (Anti D) should be given to Rh D negative women who have no preformed anti-D antibodies during pregnancy if they experience a “sensitising” event in which there is a risk of foetal blood crossing into the maternal circulation.

The administration Anti-D has been shown to result in a significant reduction in the incidence of Rh isoimmunisation.

It is important to check Rhesus D antigen and antibody status in all with a negative blood group.

Anti D should be administered within 72 hours for successful immunoprophylaxis after the appropriate sentinel event.

If this time frame is missed a dose up to 10 days may still provide some protection.

Blood should be taken from the mother before administration of the Rh D immunoglobulin to confirm her blood group and in more severe cases to assess the magnitude of foeto-maternal transfusion by Kleihauer testing, in order to determine if increased doses of anti-D are required.

Around 15% of women in Australia have a Rhesus-negative blood group, of which 40% will carry a Rhesus-negative baby.

Pathology

As little as 0.1 ml of Rh (D) positive foetal blood can result in maternal iso-immunization. 2

Preparations

Rh (D) Immunoglobulin-VF (for IM dosing):

  • 250 IU the (50 mcg, “minidose”) protects against immunization of up to 2.5 mls of foetal red blood cells.
  • 625 IU (or 125 mcg) protects against immunization of up to 6 mls of foetal red blood cells.

Rhophylac (human Anti-D CSL Behring) immunoglobulin solution for IV or IM injection.

  • Glass syringe pre-filled with 1500 IU (300μg) 2mL solution for IV injection
  • Dose in FMH: 1500 IU (300μg) vial will suppress the immunizing potential of <15mL of Rh (D) positive red cells.
  • Maximum dose 15,000 IU (3000μg), independent of whether the transfusion volumes are  > 300mL of Rh (D) positive blood
  • Administration: 2mL (1500 IU) per 15-60 seconds; within 72 hours of complication

The use of higher or further doses should be based on quantitative assessment of feto-maternal transfusion by Kleihauer test.

For haemorrhages greater than 6 mL, the recommended dose is 100 IU per mL Rh(D) positive red blood cells.

Indications

The indications for giving Anti D immunoglobulin for potentially sensitising events include:

All Rh (D) negative women (who have not actively formed their own Anti-D) should be offered Anti-D:

In the ED setting:

1. First Trimester: give 250 IU

  • Ectopic Pregnancy
  • Miscarriage (including cases of incomplete abortion and curettage):
    • Current KEMH guidelines recommend all non-sensitised rhesus negative women should receive anti-D immunoglobulin for threatened miscarriages
    • However, many sources state that there is insufficient evidence to suggest that a threatened miscarriage before 12 weeks gestation necessitates Anti-D. 1

In cases of multiple (i.e twins or more) pregnancies where a sensitizing event occurs in the first trimester, give the 625 IU dose (rather than the 250 IU dose).

2. Beyond First Trimester: give 625 IU

  • Abdominal trauma sufficient to cause feto-maternal transfusion
  • Antepartum hemorrhages

If bleeding continues intermittently after 12 weeks, give Anti D Ig at 6 weekly intervals. 4

Outside the ED setting:

1. First Trimester: Give 250 IU

  • Termination of pregnancy
  • Chorionic villi sampling (genetic studies)

2. Beyond First Trimester: Give 625 IU:

  • Amniocentesis/ cordocentesis (genetic studies)
  • External cephalic version of a breech presentation, (whether successful or not).
  • Routine antenatal dosing for Rh negative mothers:
    • All Rh (D) negative women (who have not actively formed their own Anti-D) at approximately 28 weeks gestation and again at approximately 34 weeks gestation.
    • Post-natally, within 72 hours: all women who deliver an Rh (D) positive baby should have quantification of feto-maternal haemorrhage to guide the appropriate dose of anti-D prophylaxis.

Contraindications/ Precautions

  1. Women with preformed anti-D antibodies, except where the preformed Anti-D is due to the antenatal administration of Rh (D) immunoglobulin. If there is doubt, administer Rh (D) immunoglobulin.
  2. An Rh(D) positive individual.
  3. Use caution in patients with a history of prior systemic allergic reactions following the             administration of human immunoglobulin preparations.

Anti -D is a blood product, informed consent must be obtained from the patient before administration.


References

FOAMed

Publications

Fellowship Notes

Dr Jessica Hiller LITFL Author

Doctor at Sir Charles Gairdner Hospital in Western Australia. Graduated from Curtin University in 2023 with a Bachelor of Medicine, Bachelor of Surgery. I am passionate about Obstetrics and Gynaecology, with a special interest in rural health care.

Dr Lucy J Yarwood LITFL author

MSc, MBChB University of Manchester. Currently doctoring in sunny Western Australia, aspiring obstetrician and gynaecologist

Physician in training. German translator and lover of medical history.

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