ABO Incompatibility occurs when a mother’s blood type and her baby’s blood type are not the same. There are four different types of human blood: A, B, AB, and O. Your blood type is genetic and cannot be changed. When blood must be mixed (such as during a blood transfusion or during pregnancy), it is best that the blood types are the same. While healthcare providers make sure the blood types match during a transfusion, they cannot control what blood type a baby will have. A baby’s blood type will be based on the baby’s genes.
A mother’s blood and her baby’s blood mix as a normal part of pregnancy. This can happen via the placenta (the structure that connects a mother and her baby in the womb) or during birth. Most of the time, this does not cause a problem.
However, if a mother has a different blood type from her baby, the baby’s immune system may think that the mother’s blood is harmful. It will then mount a response to rid the mother’s blood from the baby’s body, like the immune response to fight off a bacterial or viral infection. The baby’s immune system will attack the mother’s blood cells and break them down.
The most common symptom of ABO incompatibility is called jaundice. This is the medical term for when a baby’s skin and the whites of their eyes appear yellow. It usually appears in the first 24 hours after the baby’s birth. ABO incompatibility can also cause some abnormalities on routine blood tests done right after birth.
The most common risk factors for ABO incompatibility are:
The diagnosis is made by blood tests requested by a healthcare provider when they first notice the baby’s symptoms of jaundice.
Severe complications are very rare, but can include generalized swelling, life threatening anaemia, bilirubin building up in the brain causing damage, enlarged liver or spleen, or death.
A healthy pregnancy is the best way to help your baby start life off right. Since ABO incompatibility rarely has severe complications, there are no specific preventive measures for it.