Immune system response
A person who is Rh-negative (whose blood cells do not have the Rh factor) may have an immune reaction if Rh-positive blood cells enter their bloodstream. This can happen during a miscarriage, an abortion or childbirth. This is because blood from an Rh-positive baby may enter the bloodstream of an Rh-negative mother.
The mother’s body considers the Rh-positive cells a threat and mounts an immune system response. Her immune system makes antibodies (called anti-D antibodies) against the Rh-positive blood cells. If the mother conceives another Rh-positive baby, her anti-D antibodies will attack her unborn baby’s red blood cells. This complication of pregnancy is called Haemolytic Disease of the Dewborn (HDN) or ‘Rh (D) Disease’.
A pregnancy affected by Rh disease should be closely monitored. In some cases, medical treatment may include one or more blood transfusions for the unborn baby.
HDN affects the second baby
HDN rarely affects the first pregnancy. However, HDN can affect any later Rh-positive fetuses.
In severe cases, the unborn baby’s blood cannot carry oxygen and the baby dies of heart failure. This explains why fetuses affected by HDN may be miscarried or stillborn.
Babies can survive!
If the baby survives, it may be born with anaemia and jaundice. Jaundice causes a yellowish tinge to the skin and eyes, caused by an excess of the chemical called Bilirubin. The baby’s liver makes bilirubin as it breaks down the damaged or destroyed red blood cells. High levels of bilirubin can be toxic.
However, some Rh-positive babies born to Rh-negative mothers are either healthy or have mild anaemia that is easily treated.
Treatment of HDN
The preferred medical treatment for a baby born with HDN is blood transfusion. The baby’s damaged blood is regularly replaced in small amounts with compatible donor blood. The blood exchange continues until the baby’s blood has been completely replaced with healthy donor blood. The transfusion also removes maternal anti-D antibodies, which prevents damage to the baby’s new red blood cells.
Prevention of HDN
A vaccine against HDN has been available for about 40 years. The vaccine helps to prevent the mother’s immune system from making anti-D antibodies and offers protection for future pregnancies against Rh disease. Studies show that about 99 per cent of Rh-negative mothers do not make anti-D antibodies after receiving the vaccination.
Since vaccination was first introduced, the death rate from HDN in developed countries has dropped significantly. The vaccine, which contains anti-D immunoglobulin, is given as an injection to the Rh-negative mother during pregnancy and after she gives birth to an Rh-positive baby.
Rh-negative women should also be vaccinated if there has been any possibility of fetal blood entering their bloodstream. For example after:
Abdominal trauma during pregnancy
Manipulation of a breech presentation during delivery.
A mother who is Rh-positive does not need the vaccine because her pregnancies carry no risk of Rh incompatibility.
Have a test before your next pregnancy – even if you’ve been vaccinated. If you’re an Rh-negative mother and you’ve given birth to an Rh-positive child, you should see your doctor before conceiving again, even if you have been vaccinated. A blood test can detect the level of anti-D antibodies in your blood.