How does anti d injection work?

Answer 1

There are times in all pregnancies where blood from the mother and the baby may mix. This occasionally happens for no reason or it might be caused by a small placental bleed (occurring after 12 weeks of pregnancy). If both mother and baby have the same rhesus status, i.e. they are both RhD-positive or both RhD-negative, this causes no problem. However if an RhD-negative mother is carrying a RhD-positive baby, your immune system may react to the baby's blood as if it were a "foreign invader" and produce antibodies against it.

Once these antibodies are made, they cannot be removed, and in subsequent RhD-positive pregnancies they may attack and destroy the baby's red blood cells, causing anaemia, jaundice, or liver or heart problems. Blood transfusions to your baby before or after birth are needed in severe cases. These problems can be prevented by giving RhD-negative mothers an injection of anti-D immunoglobulin after any bleeding, and again after the birth of RhD-positive babies. This is known as anti-D prophylaxis.

The National Institute of Health and Clinical Excellence (NICE) also recommends routine anti-D given at 28 weeks (or between 28 and 30 weeks) to all RhD-negative mothers to prevent antibodies being produced following small silent bleeds, which happen in about 1 to 1.5 per cent of all pregnancies. Depending on the area you live in you may be given anti-D injections in two doses at 28 and 34 weeks.

Anti-D is manufactured from the plasma of human blood, and as with all blood products, there is a tiny possibility of viruses being transmitted from donor to woman. This happened in Ireland in the 1970s, when a small number of women are thought to have contracted hepatitis C through anti-D. This is extremely unlikely to happen today to women in the UK. The manufacture of anti-D is strictly controlled. All donors are screened for hepatitis B and C, and HIV, and blood is only imported from countries - mostly the USA - free of variant CJD. The chance of contracting a virus through anti-D has been estimated to be 1 in 10,000 billion doses.

Occasionally anti-D can cause a local reaction at the site of the injection or an allergic reaction in the mother, but this is rare. For this reason it is advisable to stay in the health centre or doctor's surgery for 20 minutes after having the injection.

Anti-D cannot harm your baby and the injection at 28 weeks (or in some areas at 28 and 34 weeks) is strongly recommended. If, however, you decide against this, you will still be offered the injection if you have any bleeding in the later weeks of your pregnancy and again after the birth if your baby is found to be RhD-positive.