Rhesus disease can largely be prevented by having an injection of a medication called anti-D immunoglobulin.

This can help to avoid a process known as sensitisation, which is when a woman with RhD negative blood is exposed to RhD positive blood and develops an immune response to it. 

Blood is known as RhD positive when it has a molecule called the RhD antigen on the surface of the red blood cells.

Read more about the causes of rhesus disease.

The anti-D immunoglobulin neutralises any RhD positive antigens that may have entered the mother's blood during pregnancy. If the antigens have been neutralised, the mother's blood won't produce antibodies.

You'll be offered anti-D immunoglobulin if it's thought there's a risk that RhD antigens from your baby have entered your blood – for example, if you experience any bleeding, if you have an invasive procedure (such as amniocentesis), or if you experience any abdominal injury.

Anti-D immunoglobulin is also administered routinely during the third trimester of your pregnancy if your blood type is RhD negative. This is because it's likely that small amounts of blood from your baby will pass into your blood during this time.

This routine administration of anti-D immunoglobulin is called routine antenatal anti-D prophylaxis, or RAADP (prophylaxis means a step taken to prevent something from happening).

The 2 ways you can receive RAADP are a:

• 2-dose treatment: where you receive 2 injections; 1 during the 28th week of your pregnancy and the other during the 34th week
• 1-dose treatment: where you receive an injection of immunoglobulin at some point during weeks 28 to 30 of your pregnancy

There doesn't seem to be any difference in the effectiveness between the 1-dose or 2-dose treatments. Your local integrated care board (ICB) may prefer to use a 1-dose treatment, because it can be more efficient in terms of resources and time.

RAADP is recommended for all pregnant RhD negative women who haven't been sensitised to the RhD antigen, even if you previously had an injection of anti-D immunoglobulin.

As RAADP doesn't offer lifelong protection against rhesus disease, it will be offered every time you become pregnant if you meet these criteria.

RAADP won't work if you've already been sensitised. In these cases, you'll be closely monitored so treatment can begin as soon as possible if problems develop.

After giving birth, a sample of your baby's blood will be taken from the umbilical cord. If you're RhD negative and your baby is RhD positive, and you haven't already been sensitised, you'll be offered an injection of anti-D immunoglobulin within 72 hours of giving birth.

The injection will destroy any RhD positive blood cells that may have crossed over into your bloodstream during the delivery. This means your blood won't have a chance to produce antibodies and will significantly decrease the risk of your next baby having rhesus disease.

Some women are known to develop a slight short-term allergic reaction to anti-D immunoglobulin, which can include a rash or flu-like symptoms.

Although the anti-D immunoglobulin, which is made from donor plasma, will be carefully screened, there's a very small risk that an infection could be transferred through the injection.

However, the evidence in support of RAADP shows that the benefits of preventing sensitisation far outweigh these small risks.