ABO Haemolytic Disease of Newborn
ABO haemolytic disease of newborn is a blood disorder that occurs when a mother and baby have incompatible blood types from the ABO blood group system. Unlike other forms of this condition, it can affect a firstborn baby and typically causes milder symptoms than similar blood group disorders.
Table of contents
- What is ABO haemolytic disease of newborn?
- What causes this condition?
- Who is at risk?
- Signs and symptoms
- How is it diagnosed?
- Treatment options
- Possible complications
What is ABO haemolytic disease of newborn?
ABO haemolytic disease of newborn (also known as ABO HDN) is a blood disorder where a mother’s antibodies pass through the placenta and attack her baby’s red blood cells. This happens when the mother and baby have different blood types from the ABO blood group system.[1][2]
The term “hemolytic” means the breaking down of red blood cells. When red blood cells are destroyed too quickly, the baby can develop problems such as anemia (a low number of red blood cells) and jaundice (yellowing of the skin and eyes).[3]
This condition is different from other types of blood incompatibility diseases because it can occur in a first pregnancy. About half of all cases of ABO HDN happen in firstborn babies. Another important difference is that ABO HDN does not typically become more severe in later pregnancies.[2]
Although about one-fifth of all pregnancies involve ABO incompatibility between mother and baby, only a very small number develop symptomatic ABO HDN. The condition is relatively mild compared to other forms of blood group incompatibility.[2]
What causes this condition?
Everyone has a blood type—A, B, AB, or O—based on small substances called antigens on the surface of red blood cells. ABO haemolytic disease happens when a mother and baby have different, incompatible blood types.[4]
The condition typically occurs when a mother has blood type O and her baby has blood type A or blood type B. Mothers with blood group O are more likely to have antibodies of a type called IgG, which can cross the placenta to the baby. These antibodies attack the A or B antigens on the baby’s red blood cells.[2]
Although very uncommon, cases have been reported in babies born to mothers with blood type A or blood type B as well.[2]
There are two main ways mothers develop these IgG antibodies. First, exposure to A-antigens and B-antigens in the environment—which are widespread in nature—usually leads to production of one type of antibody, but occasionally the body produces the IgG type that can cross the placenta. Second, some mothers may become sensitized when their baby’s incompatible red blood cells cross into the mother’s bloodstream during pregnancy or delivery.[2]
Who is at risk?
ABO haemolytic disease generally develops only in specific blood type combinations. The most common scenario is when the mother has blood type O and the father has blood type A, B, or AB. If the baby inherits the father’s A or B blood type, incompatibility can occur.[2]
In about one-third of all ABO incompatible pregnancies, maternal IgG antibodies pass through the placenta to the baby, leading to a weakly positive test result on the baby’s blood. However, only a small portion of these babies develop ABO HDN symptoms.[2]
ABO HDN is generally mild and short-lived for two important reasons. First, the antibodies that enter the baby’s circulation find A or B antigens on many different types of cells in the baby’s body, not just red blood cells. This means fewer antibodies are available to attack the red blood cells. Second, during pregnancy, the baby’s red blood cell surface antigens are not fully developed, so there are fewer places for antibodies to attach and cause damage.[2]
Signs and symptoms
During pregnancy, mothers typically do not notice any symptoms of ABO HDN. The signs usually appear in the newborn baby after birth.[3]
The most common symptoms in affected newborns include pale skin, yellowing of the skin and eyes (jaundice), and yellowing of the umbilical cord. Some babies may have an enlarged liver or spleen, or severe swelling of the body.[3]
As red blood cells break down, they release a substance called bilirubin, which is brownish yellow in color. Babies have difficulty getting rid of bilirubin, and it can build up in their blood, causing the skin to appear yellow. This buildup is called hyperbilirubinemia.[3]
When a baby’s body cannot cope with anemia, the heart may begin to fail and large amounts of fluid can build up in the tissues and organs. This serious condition is called hydrops fetalis.[3]
How is it diagnosed?
Routine blood tests during pregnancy (called indirect Coombs tests) do not screen for ABO HDN. If IgG antibodies against A or B blood types are found in a pregnant woman’s blood, they are not usually reported because they occur commonly in people with blood type O.[2]
After birth, doctors may perform several tests if they suspect ABO haemolytic disease. These can include a complete blood count to check the number of red blood cells, bilirubin level tests to measure jaundice, and blood typing to confirm the mother’s and baby’s blood types. A direct Coombs test on the baby’s blood may show a weakly positive result.[2][4]
Treatment options
Babies with ABO haemolytic disease may be treated in several ways depending on the severity of their condition.[4]
For mild cases, treatment may include feeding the baby often and providing extra fluids. Light therapy, also called phototherapy, uses special blue lights to help convert bilirubin into a form that is easier for the baby’s body to eliminate. This is one of the most common treatments for jaundice.[4][7]
In some cases, doctors may give the baby antibodies through an intravenous line (IVIG) to help protect the baby’s red blood cells from being destroyed. Medicines may also be given if blood pressure drops too low.[4]
For severe cases, an exchange transfusion may be necessary. This procedure involves removing a large amount of the baby’s blood, including the extra bilirubin and antibodies, and replacing it with fresh donor blood. Simple blood transfusions without exchange may also be needed and might need to be repeated after the baby goes home from the hospital.[4]
Possible complications
While ABO haemolytic disease is generally milder than other forms of blood incompatibility, complications can occur if the condition is not properly managed.[2]
High bilirubin levels at birth or rapidly rising bilirubin can lead to prolonged hyperbilirubinemia. If bilirubin levels become extremely high, the substance can spill into the brain, potentially causing a serious condition called kernicterus, which can lead to permanent brain damage, hearing problems, deafness, or cerebral palsy.[2][3]
Other possible complications include hemolytic anemia, which must not be treated with iron supplements. Late-onset anemia can persist up to 12 weeks after birth and also should not be treated with iron. Some babies may also develop neutropenia (low white blood cell count) or thrombocytopenia (low platelet count).[2]
The severity of ABO haemolytic disease varies widely. Some babies have no symptoms at all, while others require intensive treatment. With proper monitoring and treatment, most babies with this condition recover fully.[4]
