All rhesus negative women having a surgical abortion or medical abortion over 10 weeks’ gestation are offered an anti-D injection.
As well as the main blood groups (A, B, AB or O) there is a second factor called rhesus. People who are rhesus positive have a substance called D antigen on their red blood cells. People who are rhesus negative do not have the D antigen in their red blood cells.
Whether someone is rhesus positive or negative is inherited from both parents. If the person who made you pregnant is rhesus positive, then there is a chance that the fetus will also be rhesus positive.
If at any stage of pregnancy, there is mixing of your rhesus negative blood with that of the fetus which may be rhesus positive, your body’s defence mechanism, called the immune system, may form antibodies against the D antigen. These ‘anti-D’ antibodies attack red blood cells with the D antigen on them.
This mixing of blood can happen at various stages of pregnancy, including abortion. Because the antibodies stay in your system, this could harm future pregnancies if they are rhesus positive.
The anti-D injection ‘mops up’ any D antigen that may have been carried across from the fetus to your blood supply at the time of the abortion. The idea is to neutralise the D antigen from the fetus before it causes your body to produce its own natural anti-D antibodies.
If you do not have the anti-D injection, it is possible that you will produce anti-D antibodies. If you become pregnant again and the baby is rhesus positive, the anti-D antibodies might enter the baby’s circulation and attack its blood. If this were to happen, it would make the baby ill, either in the womb or after it is born. This is called haemolytic disease of the newborn, which is a very serious condition.
It is your decision whether to have the injection. However, it is strongly recommended that you do, especially if you wish to have children at any time in the future.
Some women experience short-term rashes or flu-like symptoms, but these are uncommon. Rarely or very rarely women can have aches and pains, shortness of breath, an allergic reaction, nausea/vomiting, or a fast heart rate. Anti-D is a blood product made from a part of the blood called plasma that is collected from donors. The production of anti-D immunoglobulin 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 extremely low.