ABO Blood Type Incompatibility Between Mother and Baby

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Question. When my daughter was born, she had severe jaundice and they told me that it was due to an ABO Incompatibility. I am type O+ and she is type A. She was given two transfusions of a type that did not stop her immune breakdown. Then they gave her a type O transfusion. Is it possible for a mother with type O blood to have an incompatibility with a child of blood type A? And if we were incompatible, why did they give her a type O transfusion?

My father in law is telling me that it is impossible to have an incompatibility between these two, and all I went through was for nothing. When the doctor in charge of the NICU explained what he did, he said something about that when they gave her the type A transfusion it was like feeding her my blood and more molecules break down more. When they gave her type O, I was concerned because of the ABO incompatibility. My doctor said she can have type O and that there was nothing more for the blood to fight. Is that true? Please, can you explain this to me in a way I can understand? Tanya, Bellingham, WA

A. It would only be impossible to have a reaction like this if you were type A and the baby was type O.

Understanding Blood Types

Remember that there are three main ABO genes that determine your blood type, including types A, B, AB, and O. Since babies inherit their blood type from each parent, it is possible for a mother and baby to have different blood types.

For example, a mother who is type O and a father who is type A could have a baby who is type A.

This is the same type of inheritance as many other genes and occurs because there are two genes for each blood type. So in the above example, the mother is really OO (two genes for each blood type) and the father could be either AA or AO.

And their kids will be either type A or type O.

The reason that someone with type A blood could have either two AA genes or one A and one O gene is because the O gene is recessive. The same pattern is seen with type B blood.

In addition to the ABO blood types, babies also inherit Rh factor genes from each parent. These can also cause incompatibilities if a baby is born with Rh-negative blood and the mother is Rh-positive.

ABO incompatibility

With an ABO incompatibility, a mother can make antibodies against her baby's blood type. It doesn't happen if the mother and baby have the same blood type or if the baby is type O, since, in that case, there is usually nothing to make antibodies against. The A and B blood types are actually just protein antigens on the surface of the red blood cells. Type O blood doesn't have any of these antigens, so the type A and B blood antigens will usually be seen as foreign.

These antibodies, if the mother is type O, can cross the placenta and can break down the baby's red blood cells after she is born, leading to jaundice and anemia. This condition is called Hemolytic Disease of the Newborn or erythroblastosis fetalis, and it can also be caused by having an Rh incompatibility between a baby and mother.

If a mother is type A or B and the baby has a different blood type other than type O, she can still make antibodies against the baby's red blood cells.

ABO Incompatibility Treatments

Although many children with an ABO incompatibility do not need any treatment at all, some do require extensive phototherapy if the baby is very jaundiced. This is usually continued until the mother's antibodies are cleared from the baby's body, which happens on its own after a few days.

An ABO incompatibility that leads to jaundice, anemia, and the need for transfusions can definitely happen if the mother is type O and the baby is either type A or B.

Blood Transfusions for ABO Incompatibility

Why did she get two different types of blood transfusions? The first two were likely exchange transfusions, in which much of the baby's blood is removed and type O blood is given back. If they simply gave the baby more type A blood at that time, the mother's antibodies would have just broken it down more.

There is also something called a partial exchange transfusion in which blood is removed and normal saline is given back to the baby, but that is a treatment for polycythemia, or having too much blood.

So I think that you may have the types of transfusions that she got backwards. Are you sure that they gave her the type A transfusion first and then later gave a type O transfusion?

Keep in mind that an exchange transfusion is much different than a traditional transfusion, where you are simply given extra blood.

Why did she then get another transfusion? The last transfusion was likely a regular transfusion with type A blood that matched her own blood type. This would usually be needed if she got so anemic from the ABO incompatibility that she needed extra blood. By this time, your antibodies were likely out of her system, so there was no worry that she would break down this transfused blood.

If she really got a type O transfusion later on, I guess that it could be possible that they just didn't have any type A blood available to give her. Keep in mind that type O- blood is the 'universal donor' type of blood, because it can be given to people who are type A, B, or O.

If you still aren't sure what happened to your daughter, it would likely be best to call the NICU and have the NICU attending explain things to you again. You could also ask your pediatrician to request the records from the NICU and review them for you.




Avery's Diseases of the Newborn. 9th ed. Philadelphia, PA: Elsevier Saunders; 2012

Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016

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