Information Sheet

Rhesus negative and Anti-D

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There are several blood groups including A, B, AB, and O. Blood is also either Rhesus positive or Rhesus negative. Your blood type is a combination of these two classification systems (for example B+ or O-). The Rhesus type you have depends on the blood group of both biological parents.

Why is Rhesus negative blood group important in pregnancy?

When pregnant, someone who has Rhesus negative blood, may have a fetus that is Rhesus positive. The blood type of the fetus cannot be tested until after birth.

Problems can occur when some of the blood cells from the fetus mix with your blood. This would usually only happen at the time of birth, or during an event such as a miscarriage or surgical abortion after 10 weeks’ gestation.

Your immune system will treat the blood cells from the fetus as foreign and respond by making antibodies against them. The immune system has a good memory, and this means that in any future pregnancies where the fetus is again Rhesus positive, large amounts of these antibodies can be made rapidly and may cross the placenta (the afterbirth) and destroy the fetus’ blood cells. This can cause serious complications such as severe anaemia, brain damage and even death of the fetus in some cases. This condition is known as Haemolytic Disease of the Newborn (erythroblastosis fetalis).

By giving an injection of Rhesus antibodies, known as Anti-D, the person’s immune system is stopped from making antibodies against future pregnancies, preventing Haemolytic Disease of the Newborn.

You will only be offered an Anti-D injection if you have a Rhesus negative blood group. To be effective, this must be given as soon as possible within 72 hours of a ‘sensitising’ event, such as surgical abortion after 10 weeks’ gestation, before the immune system has the chance to make its own antibodies. Medical and surgical abortion under 10 weeks are not considered to be sensitising events.

Anti-D is made from the plasma (liquid part of blood) of carefully selected blood donors from the Australian Red Cross Lifeblood. The donors and donations are screened to reduce the risk of transmitting any diseases.

Very rarely a person may be allergic to RhD immunoglobulin (antibodies). Reactions that are more common are:

• Injection site pain or irritation
• Fever
• Headache
• Dizziness
• Nausea

Everyone has the right to decide whether or not to have any treatment. Before giving consent, it is important to understand why you need the treatment and its risks and benefits for you. If you have further questions after reading this leaflet, please ask your doctor.

References
Rh(D) Immunoglobulin-VF Approved Product Information amended 14 January 2022

Guidelines for the use of Rh (D) immunoglobulin (Anti-D). RANZCOG Nov 2023