Rhesus disease and Anti-D injections

Why does my blood type matter?

You probably haven’t given your blood much thought before, but when you get pregnant, you suddenly get the full lowdown, because if you and your baby have different blood types it can cause rhesus disease.

Pregnant women who are found to be RhD negative may be offered a blood test after 12 weeks of pregnancy to test for DNA from the unborn baby and allows the baby’s blood group to be checked without any risk. If your baby is RhD negative, they’re not at risk of rhesus disease and no extra monitoring will be necessary. If they are found to be RhD positive, then routine Anti-D prophylaxis is offered in the third trimester of pregnancy as small amounts of blood from your baby may have passed into your blood. If you are RhD Negative and known to be carrying a baby who is RhD Positive or your baby’s blood group is unknown then you will be offered Routine Anti-D Prophylaxis during pregnancy and after any incident in pregnancy where blood from your baby may have passed into your blood, such as a vaginal bleed or following childbirth, to prevent rhesus disease in a future pregnancy.

If your blood type is RhD negative you will be given an Anti-D immunoglobulin routinely during the third trimester of your pregnancy as small amounts of blood from your baby will pass into your blood during this time.

This administration of anti-D immunoglobulin is called routine antenatal anti-D prophylaxis, or RAADP.

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

How do I find out if I’m rhesus negative?

At your first antenatal appointment you’ll probably have a test to find out which blood group you have  - A, B, AB or O. You’ll also find out if your blood is ‘rhesus positive’ or ‘rhesus negative’, and this is the important bit.

If you have rhesus positive blood you don’t need to do anything, but if you’re rhesus negative, you may need ‘Anti-D’ injections to protect your baby. About 15% of women are rhesus negative.  

What causes rhesus disease?

Rhesus disease can develop when you have rhesus negative blood and your unborn baby has rhesus positive blood. It’s really becomes a problem though when you’ve been ‘sensitised’ by exposure to rhesus positive blood in the past – usually during a previous pregnancy with an RhD positive baby.

Your body responds to the rhesus positive blood by producing antibodies (infection-fighting molecules) that attack the foreign blood cells. These can cross the placenta, causing rhesus disease in the unborn baby. The antibodies can also keep attacking the baby's red blood cells for a few months after birth.

What is rhesus disease?

Rhesus disease doesn't harm the mum, but it can cause the baby to become anaemic and develop jaundice. In the most severe cases it can cause stillbirth. There’s no need to worry though - rhesus disease is very uncommon these days, because it can usually be prevented by the ‘Anti-D’ injections.

Anti-D injections

A few injections of ‘Anti-D’ will stop your body from producing antibodies against your baby, and reduce the chances of you becoming ‘sensitised’ too.

When do I have ‘Anti-D injections?

You can have a one-off injection at 28-30 weeks, or two separate injections at 28 and 34 weeks. It’s all very easy – the injections take just a few seconds and are quite safe for you and your baby.

What if I’m already ‘sensitised’

If you’ve developed anti-D antibodies in a previous pregnancy, this means you’re already sensitised and the injections won't be able to help. But you and your baby will be monitored more closely than usual, both during pregnancy and when your baby is born, to keep your baby safe.

Treating rhesus disease

It’s very unlikely an unborn baby will develop rhesus disease, but if they do the treatment they receive depends on how severe it is. In extreme cases, the unborn baby may need a blood tranfusion. After delivery, the baby could be admitted to a neonatal hospital unit for newborn babies. Treatment for rhesus disease after delivery can include a light treatment called phototherapy, blood transfusions, and an injection of a solution of antibodies (intravenous immunoglobulin) to prevent red blood cells