Page modified at: 19/12/2009
ANTI-D PROPHYLAXIS FOR RHESUS D NEGATIVE WOMEN
In 2002 NICE issued guidance recommending that routine antenatal Anti-D prophylaxis be offered to all non-sensitised pregnant women who are Rhesus D (RhD) negative. Earlier the Royal College of Obstetricians and Gynaecologists issued guidance containing the same recommendation.
Anti-D prophylaxis is offered at 28 and 34 weeks to all non-sensitised pregnant women who are RhD negative. RHESUS NEGATIVE PREGNANT WOMEN
Approximately 15% of women in the UK are RhD negative. RhD negative women who carry a RhD positive fetus may produce antibodies to the fetal RhD antigens after a feto-maternal haemorrhage. These antibodies may then cross the placenta in future pregnancies and cause haemolytic disease of the fetus if it is RhD positive. A woman can also be sensitised by a previous miscarriage, spontaneous or elective abortion, or amniocentesis or other invasive procedure.
THE RHESUS FACTOR
The RhD Factor is the name given to a special protein attached to the red blood cells in the blood. 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’, those without are called ‘RhD-Negative’.
Below is an image of two red blood cells, one with the RhD Factor and one without
RhD-Positive red blood cell, RhD-Negative red blood cell HAEMOLYTIC DISEASE OF THE NEWBORN
Haemolytic Disease of the Newborn (HDN) is caused by a blood group incompatibility, and can affect RhD-positive babies born to RhD-negative mothers. During pregnancy, and in particular at the time of childbirth, small amounts of red blood cells from the RhD-positive fetus can enter the maternal circulation. When this happens, the mother produces antibodies against the baby's red blood cells to remove them from her circulation. This does not normally harm the first RhD-positive baby, but during subsequent RhD-incompatible pregnancies antibody production is accelerated and the excess antibodies cross the placenta into the baby's circulation and cause the destruction of the baby's circulating red cells
Haemolytic disease of the newborn (HND) can range in severity from being detectable only in laboratory test, through to stillbirth, birth of infants with severe disabilities or death of newborn children from an anaemia and jaundice.
Diagram domonstrating how Anti-D works
How HDN can be prevented
Anti-D IgG can prevent the mother producing anti-D antibodies by coating any of the baby's RhD-positive red cells that cross the placenta into the mother's circulation. This enables their rapid removal before they have time to 'sensitise' the mother's immune system.
For over 30 years prophylactic Anti D has been given to Rhesus D negative women at the time of a sensitising event during pregnancy and immediately after the birth if the baby is Rhesus positive. This programme has been extremely successful in reducing the mortality and morbidity in the babies of future pregnancies. However, even with this preventive measure, 1% -1.5% of Rhesus D negative women still develop antibodies during pregnancy.
ROUTINE ANTENATAL ANTI-D PROPHYLAXIS (RAADP)
A number of studies have now shown that routine antenatal Anti-D prophylaxis can reduce sensitisation to around 0.3%, resulting in around four times fewer women becoming sensitised and consequently a reduction in fetal deaths and disability. This reduction in affected babies will result in considerable savings in terms of the requirement for special care and intensive care for these babies at birth, as well as the care for those with any long-term disability, including neurological and developmental problems.
WHAT IS THE DIFFERENCE BETWEEN RAADP AND PROPHYLACTIC ANTI-D
The difference between RAADP (ie routine prophylaxis at 28 and 34 weeks) and prophylactic Anti-D given because of likely sensitisation should be clearly explained to the woman.
* A woman’s use of RAADP at 28 and 34 weeks should not be affected by whether she has already had antenatal Anti-D prophylaxis(AADP) for a potentially sensitising event early in pregnancy.
* A woman’s use of post-partum Anti-D prophylaxis should similarly not be effected by whether she has had RAADP or AADP as a result of a sensitising event.
The guidance produced by NICE for England and Wales states:
* It is recommended that routine antenatal Anti-D prophylaxis (RAADP) is offered to all non-sensitised pregnant women who are RhD negative.
* The clinician (obstetrician, midwife or general practitioner) responsible for the prenatal care of a non-sensitised RhD negative woman should discuss with her RAADP and the options available so that the woman can make an informed choice about treatment.
This discussion should include the circumstances where RAADP would be neither necessary nor cost effective. Such circumstances might include those where the woman: - has opted to be sterilised after the birth of the baby - is in a stable relationship with the father of the child, and the father is known to be, or found to be, RhD negative - is certain that she will not have another child after her current pregnancy.
National Institute for Health and Clinical Excellence
WHERE CAN I GET FURTHER INFORMATION?
A full copy of the guidance can be obtained from the NICE website.
Routine Anti-D prophylaxis is offered at 28 and 34 weeks as two separate intramuscular injections to all non-sensitised pregnant women who are Rhesus D negative. A Growth scan would also be carried out at each visit to ensure the general wellbeing of the baby.