Download The Rhesus factor and anti-D

The Rhesus factor and anti-D
Information for women and their families
What is rhesus negative blood?
Everybody’s blood belongs to one of four main blood groups: Group A, Group O, Group B, Group
AB which are carried on the red blood cells. Each of these groups may be RhD positive or RhD
negative.
About 85% of people have the RhD factor, the other 15% do not. People whose red blood cells
carry the factor are called RhD positive (or Rhesus positive), those without are called RhD
negative (or Rhesus negative).
How can the Rhesus factor affect pregnancy?
Sometimes during pregnancy a small amount of blood can cross over from the baby’s circulation in
the placenta and enter the mother’s bloodstream. This generally happens just before the birth
and is quite normal, occurring in nearly 75% of all pregnancies. However, such a transfer of blood
is also likely to occur after a particular event such as a miscarriage or an amniocentesis (needle
test for Down’s syndrome).
If this transfer of blood occurs from a Rhesus positive baby to a Rhesus negative mother then
the mother’s immune system will see the baby’s blood as ‘foreign’ and may produce antibodies
against the baby’s blood cells in the mother’s circulation. The mother’s immune system retains the
memory of how to make these antibodies, which gives her the ability to make them more quickly
and in greater numbers in the future if required.
This only becomes a problem during the next pregnancy if the baby is again Rhesus positive and
there is another transfer of the baby’s blood across the placenta. The mother’s immune system
uses its memory to make the same antibodies as before. These can then recross the placenta and
start to destroy the baby’s blood within the baby’s circulation before birth.
Babies who have this problem are said to have Haemolytic Disease of the Newborn, or HDN for
short.
HDN can be very mild and only detectable by laboratory test. But it can be more serious and
cause the baby to be stillborn, jaundiced, severely disabled, or to die after birth as a result of
anaemia. In England and Wales, about 500 babies develop HDN each year, and must be closely
monitored. Each year about 25 to 30 babies die from HDN, and a further 30 will have minor
developmental problems.
How can protection be provided?
Doctors and midwives are very aware of this problem and can prevent it from happening by giving
the Rhesus negative mother an injection of anti-D immunoglobulin (anti-D for short) to prevent a
woman producing antibodies against RhD-positive blood cells. This will then prevent the
development of HDN in an unborn baby. This is known as anti-D prophylaxis. Prophylaxis is the
word for a treatment that is used to prevent something happening.
When is anti-D given?
Anti-D may be given in three situations:
1. Antenatal anti-D prophylaxis (AADP) for a potentially sensitising event. Baby’s blood
cells can enter the mother’s circulation if something happens during the pregnancy such as
a miscarriage, termination, an amniocentesis, vaginal bleeding, and external cephalic version
(turning a breech baby head down). An injection of anti-D may be given to RhD negative
women after such an event.
2. Routine antenatal anti-D prophylaxis (RAADP). Since 2002 the National Institute of
Clinical Excellence (NICE) has recommended that routine antenatal anti-D prophylaxis is
offered to all pregnant women who are RhD negative if they have not already been ‘sensitised’. If you are already ‘sensitised’ this means that you already have antibodies to the
D antigen in your blood that can be detected by a blood test at the beginning of your pregnancy. RAADP is given by injection to RhD negative pregnant women at 28 weeks of the
pregnancy. You should be offered RAADP even if you have already had AADP for a
potentially sensitising event earlier in your pregnancy.
3. Postnatal anti-D prophylaxis (PADP). After the birth a blood sample will be taken from the
cord to test the baby’s blood group. If the baby is RhD positive, a mother who is RhD
negative will be given a further injection of anti-D. This injection will remove any of the baby’s
RhD positive red cells that may enter the mother’s circulation. You should be offered
postnatal anti-D prophylaxis whether or not you have had AADP or RADDP.
What are the risks of having anti-D?
Anti-D immunoglobulin is made from a part of the blood called plasma that is collected from fully
screened blood donations from the USA. The production of anti-D is very strictly controlled to
ensure that the chance of a known virus being passed from the donor to the person receiving the
anti-D is very low - it has been estimated to be one in 10,000 billion doses.
Occasionally anti-D prophylaxis causes allergic responses in the mother, but these are rare.
Do I have to have anti-D injections?
No, the choice is yours. However the aim is to reduce the risk of HDN to your future children.
In some situations, anti-D may not be necessary. Such situations might include the following:
• you have opted to be sterilised after the birth of the baby
• you are in a stable relationship with the father of the baby, and you are certain that the father
is RhD negative; please ask if you want your partner’s blood group checked
• you are certain that you will not have another baby after the current pregnancy.
The Rhesus factor and anti-D, August 2015
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References
1. Royal College of Obstetricians and Gynaecologists. Use of anti-D immunoglobulin for RH
prophylaxis - Guideline No 22. RCOG: London 1999.
2. NICE. Routine antenatal anti-D prophylaxis for women who are rhesus D negative. NICE:
London, August 2008 (NICE technology appraisal guidance 156).
www.nice.org.uk/nicemedia/pdf/TA156Guidance.pdf
What if I have any further queries or concerns?
Your midwife or doctor will be happy to tell you more about the Rhesus factor and what it means to
you. If you have any questions, or if you have any doubts about the injection, do not be afraid to
ask.
Alternatively please contact the Maternity Day Care at either:
• William Harvey Hospital, Ashford Telephone: 01233 616638
• Queen Elizabeth the Queen Mother Hospital, Margate
Telephone: 01843 234483
The Rhesus factor and anti-D, August 2015
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Any complaints, comments, concerns, or compliments
If you have other concerns please talk to your doctor or nurse. Alternatively please contact our
Patient Advice and Liaison Service (PALS) on 01227 783145 or 01227 864314,
or email [email protected]
Further patient information leaflets
In addition to this leaflet, East Kent Hospitals has a wide range of other patient information leaflets
covering conditions, services, and clinical procedures carried out by the Trust. For a full listing
please go to www.ekhuft.nhs.uk/patientinformation or contact a member of staff.
After reading this information, do you have any further questions or comments? If so,
please list below and bring to the attention of your nurse or consultant.
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are therefore happy to provide the information in this leaflet in
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responsible for your care.
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This leaflet has been produced with and for women and their families
Information produced by Women’s Health
Date reviewed: August 2015
Next review date: August 2017
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