Blood Group & Antibodies
This leaflet explains the tests that can be done during pregnancy to:
- find out your blood group;
- find out your Rhesus group; and
- look for antibodies.
The people looking after you during your pregnancy need to know your blood group in case you ever need a blood transfusion. It is also important to know your Rhesus group.
What is your Rhesus group?
What are red cell antibodies?
If you are Rhesus negative
Can haemolytic disease of the newborn (HDN) be prevented?
Results
Why should I be offered an anti-D injection?
What is your Rhesus group?
Your blood group will usually be one of the following four main groups:
- group O;
- group A;
- group B;
- group AB.
You also have another blood group called the Rhesus group. You can be either Rhesus positive or Rhesus negative. For example, your overall blood group might be written as ‘group O Rhesus positive’.
What are red cell antibodies?
Antibodies are your body’s natural defence against anything that your body thinks is foreign. Red cells carry oxygen in your blood. You may form antibodies if blood cells with a different blood group from your own enter your bloodstream. This can happen because of a blood transfusion or from your baby during pregnancy.
Red cell antibodies can pass from your bloodstream into your baby's. This can damage your baby's blood. Sometimes it causes a rare condition called haemolytic disease of the newborn (HDN). Symptoms of HDN include jaundice and anaemia (lack of red blood cells). Affected babies usually need to be admitted to hospital and treatment includes phototherapy (treatment with light) and sometimes blood transfusions.
If you are Rhesus negative
If you are Rhesus negative and your baby is Rhesus positive, then your body might produce antibodies to destroy these 'foreign' Rhesus positive blood cells. This sometimes happens during pregnancy, or more likely when your baby is delivered. If you are Rhesus positive, this problem does not usually happen.
Can haemolytic disease of the newborn (HDN) be prevented?
To help prevent HDN, if you are Rhesus negative you will be offered an injection or injections of anti-D immunoglobulin during pregnancy and after delivery if the baby is Rhesus positive. This can help stop your body making Rhesus antibodies and reduces the risk of problems in future pregnancies.
What is anti-D immunoglobulin?
Anti-D immunoglobulin (injection) is a blood product made from blood collected from donors.
Is anti-D immunoglobulin safe?
Occasionally anti-D immunoglobulin causes allergic reactions. How it is produced is very strictly controlled so the risk of a known virus being passed on to you from the donor is very low.
What are the advantages of having screening for my blood group and antibodies?
You will be offered a blood test early in your pregnancy. If you have this test, you will know your blood group and whether you are Rhesus positive or Rhesus negative. It is less common to be Rhesus negative. About 15% (15 out of a hundred) of the population are Rhesus negative.
The test will also look for antibodies. It is important to know about these so if you ever need a blood transfusion this could be given safely. Rarely, antibodies present in your blood might carry the risk of affecting your baby as explained above. If this happens you and your baby can be given specialist care. This blood test is offered to you again around the 28th week of your pregnancy.
What are the disadvantages of having screening for my blood group and antibodies?
Screening is a simple blood test. The only risk would be the same as having any blood test.
Where will the test be done?
Your midwife will tell you where you can have the test done.
Results
Will my result be confidential?
The NHS keeps the results of all tests confidential. Hospital policies vary on how many people have access to your test results. Your midwife will be able to explain the local arrangements to you.
How will I get the result of my screening test?
Your midwife will tell you how and when you will get the result of the test. You should receive the result of your blood test within three weeks of having your blood taken.
Diagnostic tests for blood group and red cell antibodies
The screening test for blood group and red cell antibodies is very accurate. Sometimes you will need extra blood tests if a problem is suspected or found.
If you know that you are Rhesus negative
Contact your midwife or doctor as soon as possible to remind them that you are Rhesus negative if:
- you have vaginal bleeding after 12 weeks;
- you have a miscarriage after 12 weeks; or
- you suffer an injury to your abdomen (for example, an injury from a seat belt in a car accident or by falling over).
If any of these things happen, your body may start to produce antibodies and you may need an anti-D injection.
Why should I be offered an anti-D injection?
You should be offered an anti-D injection to reduce the risk of you producing antibodies. You should also be offered an anti-D injection in any of the following circumstances:
- You have an amniocentesis.
- You have chorionic villus sampling.
- When your baby is delivered (usually only if the baby is Rhesus positive).
- You have an ectopic pregnancy.
- You end your pregnancy.
Remember to tell any health care professional looking after you that you are Rhesus negative.
They will check your antibody level throughout your pregnancy. You may also be offered anti-D injections while you are pregnant to try and prevent problems.
More information
You can get more information about being Rhesus negative from your midwife or your hospital doctor (your obstetrician).
Blood Groups and Red Cell Antibodies in Pregnancy Leaflet. Available at: http://hospital.blood.co.uk/library/patient_information_leaflets/leaflets/index.asp (Accessed on 22/09/09)
© Copyright 2010 Public Health Wales NHS Trust. All rights reserved. Not to be reproduced in whole or part without the permission of the copyright owner. www.antenatalscreening.org April 2010 BG 9th Edition |
