All pregnant women are screened and reviewed during their pregnancy to establish their ABO and RhD blood group and identify if there are any red cell antibodies in their blood. These antibodies destroy red blood cells that are different from their own. If antibodies are detected, they are monitored by regular blood testing and the results will guide any necessary treatment for a complication known as haemolytic disease of the foetus and newborn (HDFN). This is caused by antibodies from the mother crossing the placenta and attacking red cells in the unborn baby. If someone is RhD negative, they may be given injections of RhD immunoglobulin during their pregnancy to stop the mother’s anti-RhD antibodies attacking the red blood cells in the unborn baby.
Why get tested?
Blood cells are classified according to the different proteins or antigens that are on the surface of your blood cells. This is explained fully in the section on Blood Groups.
The RhD antigen is important if you are pregnant. If you are RhD negative but the father is RhD positive, your unborn baby may also be RhD positive. Sometimes, RhD negative mothers may produce antibodies to the RhD antigen if the baby is RhD positive. This antibody is known as anti-D and can cause destruction of foetal and neonatal red cells, a condition known as haemolytic disease of the foetus and newborn (HDFN).
To prevent RhD negative mothers producing anti-D, prophylactic RhD immunoglobulin injections are given routinely during pregnancy.
Other antibodies may also develop if you and your baby have different blood group antigens. These need to be identified and may also be monitored during your pregnancy if the antibody present can cause HDFN.
To ensure that these complications do not arise, a test called an antenatal group and screen is used routinely by a midwife or doctor to:
If red cell antibodies are detected, these are monitored by regular blood testing and the results will guide any necessary treatment for possible HDFN.
In severe cases of HDFN, the baby may be born with severe anaemia and/or severe neurological damage caused by high levels of bilirubin (jaundice). Occasionally HDFN may be fatal.
Having the test
If you are tested and found to be RhD negative, you may be given injections of RhD immunoglobulin (anti-D) during your pregnancy and after delivery of the baby to neutralise the effect of any of the baby’s red cells in your circulation.
If red cell antibodies are detected, you will be regularly monitored during your pregnancy to guide any necessary treatment for potential HDFN.
Questions to ask your doctor
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:
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