Every individual has a different blood type, which is made up of the ABO system. There are four main blood types, which have antibodies and antigens. In addition to that, each blood type has another surface antigen, which means they can be either Rhesus D positive or Rhesus D negative. This is important to know if, for example, you need a blood transfusion in the case of an operation or an accident. Certain blood types may be incompatible to be transfused with other blood types. In a similar way, it’s really important in pregnancy, if a woman is one particular blood group, and her unborn baby is another. It can result in severe complications unless treatment is given.
If a Rhesus negative mother Is pregnant with a Rhesus negative baby, there’s no problem. If the same mother is pregnant with a Rhesus positive baby, this is harmless for the current pregnancy, but it poses a risk for the second and any future pregnancies. The woman’s immune system sees the Rhesus positive components (antigens) as a threat, and responds by producing defending immune components called antibodies. These will be ready to fight any future pregnancies that are Rhesus positive babies, potentially causing harm. This may lead to a condition called Rhesus disease of the newborn. There is no risk if the mother is Rhesus positive and she has a Rhesus positive or Rhesus negative baby.
In Rhesus disease the antibodies from the mother cross the placenta and attack the red blood cells of the unborn baby. This can continue until shortly after baby is born. In the womb this results in anaemia in your newborn, as mum's antibodies destroy baby's red blood cells. Anaemia, jaundice (yellowing of the skin due to damage of the liver) and reduced muscle tone may be evident once the baby is born.
Anaemia in the womb can be detected by ultrasound. It is important to treat Rhesus disease immediately, as it can result in stillbirth, brain damage, learning disabilities and physical disabilities such as blindness. In severe cases, the unborn child may need transfusion in the womb. After delivery, the newborn child may need admission to the baby unit and a combination of treatments including blood transfusions, light therapy and injection of antibodies to prevent further destruction. Correct and prompt treatment is effective at preventing further complications.
It is very important to attend all your antenatal appointments as scheduled, as you will have your blood tests taken to check your blood group and Rhesus status. If a woman is Rhesus D negative, she’ll be offered anti-D immunoglobulin injections throughout her pregnancy to remove Rhesus D blood cells from the foetus before the woman develops antibodies against them. If the mother already has anti-D antibodies, then she will be monitored closely throughout pregnancy and delivery, as the injections will be ineffective.