A guide to discussing Rh status with pregnant women: Antenatal Testing for Blood Group, Red Cell Antibodies and Anti-D Injection for Rh D Negative women.
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The following discussion guideline follows a useful format recommended by the 3Centres Collaboration for discussing tests and investigations offered antenatally to women with uncomplicated pregnancies and intentionally uses lay language.
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The aim of discussion prior to tests, investigations or administration of pharmaceuticals is to help women understand the following:
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- Purpose - What the test / procedure / drug specifically does or looks for
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- Reason - Why the test / procedure / drug is important
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- Method - How is the test done / drug given
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- Pros and cons - What are the considerations in terms of benefits & risks
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- Implications - What happens next given positive / negative results
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- Any questions - Address any concerns / provide more information
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- Offer - Determining if a woman would like to proceed with the test / procedure / drug
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Purpose
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At the first antenatal visit, we offer all women a test to:
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- determine their blood group
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- look for the presence of the Rh D factor (you have tested negative to this factor)
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- to detect any red cell antibodies, including the Rh D antibody (also called anti-D or Rh D immunoglobulin).
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For the majority of women, no red cell antibodies will be detected.
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About 15% of the Australian population is Rh D Negative and 85% are Rh D Positive. Breakdown by ethnicity is as follows:
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- 15-17% of Caucasians are Rh D Negative
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- < 1% of Indigenous Chinese
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Reason
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During pregnancy and childbirth, there is a risk that some of the baby's blood cells will get into the mother's blood stream and she will form antibodies against the baby's blood.
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Most of the time red cell antibodies can occur in response to:
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- previous blood transfusion
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| There are known factors that put pregnant women at risk of this occurring ie amniocentesis, but sometimes "mixing of blood" occurs unknowingly - leading to silent' sensitisation. If this occurs in pregnancy, it is most likely to occur in the third trimester. |
- Some of these antibodies, including anti-D can cross the placenta, damage the red cells of the unborn baby, causing a condition called Haemolytic Disease of the Newborn (HDN).
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- This can happen where a woman who has developed anti-D antibodies from a previous pregnancy has another Rh D positive baby.
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- Untreated babies may become anaemic, can suffer brain damage, or in severe cases death. This can happen even before birth.
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- Milder cases of anaemia result in jaundice shortly after birth.
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Incidence of isoimmunisation during pregnancy for Rh D incompatibility is about 1.5%. This can be reduced to 0.2% by giving Rh D Immunoglobulin at 28 and 34 weeks as well as post-partum.1
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It has been modelled that 5 deaths (not including handicaps) due to HDN can be averted each year Australia wide, with the administration of prophylactic anti-D (28 & 34 weeks) to primigravid women. About 8-9 further (total 14) deaths could be averted when prophylactic anti-D at 28 & 34 weeks is introduced universally.2
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Note: Giving anti-D to a woman who has developed Rh D antibodies will be of no benefit but it will not put her at extra risk.3
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 Method
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- Blood is collected for testing at the 1st pregnancy visit. The test for red cell antibodies is repeated at about 26 weeks.
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- Anti-D for Rh D negative women is offered by injection to the muscle in the arm or leg routinely at 28 and 34 weeks, and after childbirth.
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- In addition anti-D is given when there is an increased chance of baby's blood cells entering the mother's blood stream. This can occur if you have vaginal bleeding during pregnancy, during a miscarriage, abortion or termination of pregnancy or during medical procedures such as amniocentesis.
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Pros and cons
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Pros:
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- The presence of antibodies that can cause significant HDN means a woman will be offered pregnancy care by clinicians with expertise in this area.
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- You may require more frequent visits to have specialist care at the Royal Women's Hopsital.
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Women with Group 1 or Group 2 antibodies or previous history of HDN will be referred to the MFM Program for ongoing care.
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Women with Group 3 antibodies can continue routine care, as these are not considered clinically significant.
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- For Rh D antibody (which is a Group 1 antibody), giving an anti-D injection to an Rh D negative woman who has no pre-formed antibodies, can help prevent or reduce the chance of her making anti-D antibody.
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Cons:
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- Anti-D injection is a blood product and there is a very small chance that it could pass on some infections.
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- However, Anti-D is made from blood donors who are always strictly screened for their health and lifestyle whenever they give blood. The standard donor screening process only allows a blood donation if a donor is in good health, and does not have any relevant condition detectable.
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- Blood donations are then always tested for the infections HIV/AIDS, Hepatitis B and Hepatitis C. Blood donations are only used if there is no evidence of these infections. The manufacturing process for making anti-D injection is able to destroy these and many other viruses. (Offer written consumer information).
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For contraindications, precautions, and adverse effects please refer to the product information leaflet.
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NB: There is no evidence for adverse reactions resulting from Anti-D administration. Instead, the information leaflet refers to trials for Hepatitis B immunoglobulin as well as reactions from any IM injection. However, these should still be discussed.
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Implications
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- when red cell antibodies are detected, the laboratory performs special tests to determine the type of antibody
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- many antibodies do not cause significant HDN and are not a cause for concern
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- if tests show that you have produced antibodies that puts your baby at risk of HDN, the team of specialists will monitor your levels of antibody with further tests and care for your baby's health throughout the pregnancy
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Questions
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Father is believed to be Rh D Negative:
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Some Rh D negative women decline to accept anti-D where the father of the baby is thought to be Rh D Negative. Where this situation arises it is important to offer the following information:
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- There exists the possibility for the father to have a weak expression of the D factor which routine laboratory testing will not normally exclude, ie those with weak D will be classified as Rh D negative with routine testing.
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- To confirm Rh D type, the test should normally be performed on two separate samples via reference laboratory analysis.
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The woman indicates that she will not have any more children:
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Some Rh D negative women who do not wish to have any more children may decline anti-D. Where this situation arises it is recommended that the woman should understand that:
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- Unplanned pregnancies occur occasionally and could be affected if she forms anti-D. The chance of making anti-D after each Rh D positive pregnancy is about 8%.
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- If a woman becomes immunised and makes anti-D following the pregnancy and later travels to, or lives in parts of Asia or Africa, there will be considerable difficulty in providing a blood transfusion to her in most countries of these continents. Rh D negative blood is much rarer in these geographic areas.
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Concern over the safety of anti-D:
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- There is no evidence to date that the anti-D injection used in Australia (including WinRho™) has ever spread any important infections including HIV or hepatitis.
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- There is no evidence to date that either classical or the variant form of CJD (Creutzfeldt Jakob Disease) has ever been transmitted by blood products manufactured from human plasma.
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Offer
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Given a woman understands the above, determine if she accepts anti-D:
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- Where a woman declines to accept anti-D prophylaxis at 28 & 34 weeks, there is a space for an acknowledgment from her (signature) on page 6 of the Record of Pregnancy Care (MR 90097), in the Administration of Prophylactic Immunoglobulin' section.
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- The client consent / acknowledgement form for anti-D is no longer required for any anti-D.
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Further queries can be directed to the Consultant Haematologist.
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Further information
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- Cochrane Library: Use this link or link via Royal Women's Hospital library homepage (databases). Can log on free and anonymously as the hospital has a registered IP address.
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References
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1. Urbaniak, SJ. The Scientific Basis of Antenatal Prophylaxis. British Journal of Obstetrics & Gynaecology, 105 Suppl. 18:11-8, 1998.
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2. Guidelines on the prophylactic use of Rh(D) Immunoglobulin (Anti-D) in obstetrics. Main Report, National Health and Medical research Council, March 1999.
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3. Product Information-Rh(D) Immunoglobulin solution for intramuscular injection. CSL Bioplasma Ltd., November 2000.
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Royal Women's Hospital Clinical Practice Guidelines (CPGs) are intended to provide guidance to health care professionals, based on a thorough evaluation of research evidence, on the practical assessment and management of specific clinical issues or situations. The guidelines allow some flexibility on the part of the health care professional based on the needs of the specific patient for whom they are caring.
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