ABO incompatability Good rx
ABO Incompatibility in a Newborn: Why Blood Type Matters in Pregnancy
Written by Alicia Stevens, MD | Reviewed by Karla Robinson, MD
Published on April 3, 2023
print_outlinedemail_outlined
Key takeaways:
ABO incompatibility in a newborn happens when a mother and baby have incompatible blood types. Mothers with Type O-negative blood are most at risk for ABO incompatibility.
When there is a blood type mismatch in pregnancy, a mother’s immune system may begin to destroy her baby’s red blood cells. This can cause a range of health issues for the baby, from mild jaundice to severe anemia, and even lead to death.
Routine screening during pregnancy and after delivery can help find signs of ABO incompatibility. RhoGAM injections can help reduce the risk of serious problems for those at risk for blood type incompatibility.
FatCamera/E+ via Getty Images
Being an expectant parent can naturally come with some anxiety as you try to plan for and await a healthy delivery. As a result, eating a healthy diet, getting regular rest, and reducing stress may be at the top of your to-do list. But one thing you may not have considered as a potential issue in pregnancy is your blood type.
It’s possible that your blood type is not compatible with your unborn child’s blood type. This can lead to ABO incompatibility in your newborn — a condition that may have serious consequences.
What is ABO incompatibility in a newborn?
ABO incompatibility is when a pregnant mom and her baby have different blood types and that causes the mother’s immune system to react. When there is a blood type mismatch, a mother’s immune system may see her baby’s blood type as foreign. This will trigger her immune system to respond with antibodies to attack the baby’s blood cells. These antibodies are then passed to the baby while they are in the womb.
This immune response can cause hemolytic disease of the newborn (HDN). This is a condition that can cause problems ranging from mild jaundice (yellowing of the skin or eyes) to severe anemia (low blood count) and death.
What causes ABO incompatibility in a newborn baby?
ABO incompatibility happens because there are special proteins (antigens) on the surface of blood cells, and these can differ between a mother and baby. Your blood type is defined by whether you have A or B antigens present on your blood cells. If you have neither A or B antigens, you have Type O blood.
Blood types are further broken down by the presence of the Rh factor protein on the surface of red blood cells. If you don’t have the Rh factor, you have a “negative” blood type. So, for example, if you have the A antigen but don’t have the Rh factor, you have Type A-negative blood.
A blood type mismatch between a mom and baby can occur because of the presence of A or B antigens in the baby’s blood. It can also occur if the Rh factor is present in the baby’s blood (Rh incompatibility). If a mom doesn’t have these antigens or Rh factor on her own blood cells, she can have antibodies to them.
Sometimes, these antibodies are already present in the mother’s blood. But with Rh incompatibility, a mother can develop antibodies after being exposed to their baby’s blood in pregnancy or during delivery. This usually doesn’t cause an issue with first pregnancies. But with future pregnancies, there’s a risk of antibodies being passed to the baby through the placenta.
Who is at risk for ABO incompatibility?
Up to 15% of pregnancies are at risk for ABO incompatibility. And there are certain factors that can make a blood type mismatch more likely, which we review below.
Type O blood
People with Type O blood are most at risk for developing ABO incompatibility in pregnancy. That’s because, if you have Type O blood, you have natural antibodies to Type A and Type B blood groups.This would make ABO incompatibility more likely if you were carrying a baby with Type A or B blood.
Rh-negative
People who are Rh-negative are at risk of developing Rh incompatibility. If you are carrying a baby who has the Rh protein on their blood cells and you are Rh-negative, your body may produce antibodies in response. And if you are Rh-negative and have Type O blood, you may have an even higher risk of antibodies appearing.
Mixing of maternal and fetal blood
The risk of blood type incompatibility increases any time the blood of a pregnant mother (maternal blood) mixes with the blood of their baby (fetal blood). This increases the mother’s exposure to antigens in the baby’s blood and makes it more likely that she’ll develop antibodies.
Situations that could cause fetal blood to mix with maternal blood include:
Miscarriage
Bleeding during pregnancy (due to problems with the placenta or uterus)
Abdominal trauma during pregnancy
Invasive testing during pregnancy (like amniocentesis)
Attempts to move the baby into a proper birthing position (like when a baby is breech)
Childbirth
Other exposure to blood antigens
There are other reasons people may be exposed to blood antigens that are not related to pregnancy. You may have been exposed to antigens if you have had:
A bone marrow transplant
A blood transfusion
An accidental needle stick
What are the signs and symptoms of ABO incompatibility?
Symptoms of ABO incompatibility can vary and range in severity. ABO incompatibility due to ABO blood groups tends to be less severe than Rh incompatibility. But the symptoms will depend on how intense the immune response is and the point in pregnancy that it occurs.
Mild ABO incompatibility
With an ABO blood group mismatch, a baby usually shows symptoms after birth. These symptoms include:
Jaundice
Elevated bilirubin levels
Mild anemia
As a baby’s blood cells are destroyed by mom’s antibodies, the baby’s bilirubin levels rise. During pregnancy, the placenta removes bilirubin from babies’ blood. And after birth, a baby’s liver can manage elevated levels of bilirubin in mild cases. But if the red blood cell destruction is more severe, the rising bilirubin levels can lead to jaundice within 24 hours of birth or mild anemia.
Severe ABO incompatibility
If the reaction occurs earlier in the pregnancy or is more severe, a developing baby may begin to have symptoms of ABO incompatibility in the womb. And erythroblastosis fetalis (swelling of the fetal organs and baby) can result.
Signs and symptoms of severe ABO incompatibility may include:
A heart rate that’s too fast
An enlarged spleen or liver
Decreased liver function
Heart failure
Respiratory problems
How is ABO incompatibility diagnosed?
All pregnant people have ABO blood group and Rh testing during routine prenatal care. If there is an Rh incompatibility suspected, you will likely have frequent lab testing throughout your pregnancy to monitor antibody levels.
Your healthcare provider can diagnose ABO incompatibility with a positive Coombs test. This is a lab test that looks for the presence of red blood cell antibodies in your baby’s blood. This test is often done after a newborn develops jaundice to figure out the cause.
Sometimes, an ultrasound is also useful in making a diagnosis of ABO incompatibility, even while the baby is still in the womb. If it’s a severe case of ABO incompatibility, your baby may show ultrasound changes like:
Swelling at the back of the neck, head, chest, or belly
Pericardial effusion (buildup of fluid around the heart)
Increased amniotic fluid
Pleural effusion (buildup of fluid around the lungs)
A thickened placenta
How is ABO incompatibility in a newborn treated?
There are multiple ways ABO incompatibility is treated. Individual treatment plans are based on the severity of the case and when the incompatibility is recognized. We review common treatments for ABO incompatibility below.
Phototherapy
Most cases of ABO incompatibility are mild and may only need to be treated with phototherapy. This treatment is usually started when a newborn’s bilirubin reaches a level of 15 mg/dL within the first 48 hours of life.
Phototherapy uses green-blue light waves to make bilirubin water-soluble. This allows bilirubin to be more easily removed through the urine or stool, lowering blood levels.
A baby needs to be exposed to phototherapy continuously, except during breaks for feeding. And it’s helpful to have their whole body (except for the eyes) exposed to the light for rapid treatment.
Exchange transfusion
If a baby’s bilirubin levels increase despite phototherapy, exchange transfusion may be needed. This involves removing any damaged or antibody-coated red blood cells from the bloodstream. These cells are replaced with healthy, donated red blood cells.
Bilirubin levels of 20 mg/dL may require exchange transfusion treatment.
Intravenous immunoglobulin
Intravenous immunoglobulin (IVIG) treatment is also sometimes used to address rising bilirubin levels. But the data is mixed on its safety and effectiveness in treating the severe complications of ABO incompatibility.
It’s unclear how IVIG works, but it appears to prevent the red cells from being destroyed by antibodies. In some cases, it decreases the length of phototherapy treatments and hospital stays, but it doesn’t always prevent the need for exchange transfusion.
Treatment during pregnancy
If the ABO incompatibility is discovered during a pregnancy and is severe, an early delivery may be recommended, if possible. If the baby is not near full-term, a blood transfusion through the umbilical cord is sometimes needed.
How can you reduce the risk of ABO incompatibility in newborns?
If you are identified as being high risk for ABO incompatibility during your pregnancy, you will need regular follow-up care. Ongoing lab testing and fetal monitoring through ultrasound will help to pick up signs of serious complications, if there are any.
If you are at risk for Rh incompatibility because you are Rh-negative, you will need treatment with RhoGAM. You will get this injection when you are 28 weeks pregnant and within 72 hours of delivering an Rh-positive baby. This injection blocks your body from making antibodies against your baby’s red blood cells. And it reduces the risk of a harmful immune response. In fact, your risk of making antibodies after getting RhoGAM treatment is less than 1%.
But, keep in mind, RhoGAM will not help with other blood group mismatches or if you already have Rh antibodies.
What are the potential outcomes of ABO incompatibility in newborns?
If recognized and treated early, newborns with ABO incompatibility tend to do very well.
If severe ABO incompatibility begins in the womb, there is a higher risk of more serious complications from anemia. These include:
Generalized edema
Ascites (buildup of fluid around the abdomen)
Heart damage
Stillbirth
When bilirubin levels are very high and go untreated after birth, babies may develop kernicterus. This is a serious neurological condition that’s caused by bilirubin buildup in the brain. Kernicterus can cause:
Cerebral palsy
Weakness
Movement disorders
Vision problems
Hearing problems
Dental problems
Severe learning disabilities
Fortunately, with the widespread use of screening, fetal monitoring, and RhoGAM for prevention, severe complications from ABO incompatibility are now rare. And they only occur in 1% of all pregnancies.
The bottom line
ABO incompatibility — when a pregnant mom and her baby have different blood types and that causes the mother’s immune system to react — occurs in up to 15% of pregnancies. But routine screening and monitoring during pregnancy and after-delivery can reduce the risk of serious problems.
Fortunately, there are treatments available when complications from ABO incompatibility do arise. And, in general, the prognosis for ABO incompatibility is good, especially when caught early.
References
American Academy of Pediatrics Subcommittee on Hyperbilirubinemia. (2004). Management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation. Pediatrics.
American Red Cross. (2021). What is the Rh factor? Why is it important?
Costumbrado, J., et al. (2022). Rh incompatibility. StatPearls.
Dean, L. (2005). Chapter 4, hemolytic disease of the newborn. Blood Groups and Red Cell Antigens.
Gomella, T., et al. (2013). ABO incompatibility. Neonatology: Management, Procedures, On-Call Problems, Diseases, and Drugs.
Hall, V., et al. (2022). Hemolytic diseases of the newborn. StatPearls.
Izetbegovic, S. (2013). Occurrence of ABO and RhD incompatibility with Rh negative mothers. Materia Socio-Medica.
MedlinePlus. (2022). Bilirubin blood test.
Myle, A. K., et al. (2021). Hemolytic disease of the newborn: A review of current trends and prospects. Pediatric Health, Medicine and Therapeutics.
Nassar, G. N., et al. (2022). Erythroblastosis fetalis. StatPearls.
Okulu, E., et al. (2022). Intravenous immunoglobulin use in hemolytic disease due to ABO incompatibility to prevent exchange transfusion. Frontiers in Pediatrics.
Porter, M. L., et al. (2002). Hyperbilirubinemia in the term newborn. American Family Physician.
Reddy, D. K., et al. (2022). Kernicterus. StatPearls.
Theis, S. R., et al. (2022). Coombs test. StatPearls.
Vanaparthy, R., et al. (2022). Hydrops fetalis.
Yoham, A. L., et al. (2022). Rho(D) immune globulin. StatPearls.
ABO Incompatibility Explained: Risks of Incompatible Blood Types - GoodRx