What Is Erythroblastosis Fetalis?

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Erythroblastosis fetalis, also known as hemolytic disease of the newborn, is an anemia that occurs in a fetus when the pregnant parent and fetus have different blood types. Major blood types are A, B, O, and AB, but blood type is also based on Rh factor, a protein found on the surface of red blood cells. 

When the birthing parent and fetus have incompatible Rh factor types, the parent’s body can attack the fetus’s red blood cells. This causes several serious complications and needs to be treated right away.

This article provides an overview of erythroblastosis fetalis, including the causes, symptoms, and treatments. 

Pregnant woman holding her bump.
JGI/Tom Grill/Getty Images

Types of Rh Factor Status 

Erythroblastosis fetalis can occur when a pregnant person lacks the Rh factor protein that the fetus has on its red blood cells. The parent's immune system can detect the Rh factor as "foreign" and mount an immune response. Most people have the Rh factor protein, making them Rh-positive. It's important to know your Rh factor, especially if giving birth more than once.

The two Rh types are:

  • Rh-positive: Rh factor is present on the surface of red blood cells.
  • Rh-negative: Rh factor is absent from the surface of red blood cells

Erythroblastosis Fetalis Symptoms

When a newborn is experiencing erythroblastosis fetalis, their red blood cells are destroyed. Symptoms of this condition may include:

  • Edema (swelling)
  • Jaundice (yellowing of the skin and whites of the eyes) 
  • Anemia (low red blood cell count)
  • Hepatomegaly (enlarged liver)
  • Splenomegaly (enlarged spleen)
  • Hydrops (fluid throughout the body tissues)


Erythroblastosis fetalis is caused by blood type incompatibility. Rh factor is a protein found on the surface of the red blood cells, responsible for carrying oxygen throughout the body. 

Most of us have Rh factor on the surface of our cells (Rh-positive). People who do not have Rh factor on their cells are considered Rh-negative. Rh status is inherited from your birth parents. 

When a pregnant parent is Rh-negative and the fetus is Rh-positive, the parent’s body will treat the fetus’s blood as a foreign substance. The parent’s immune system will develop antibodies against the fetus’s Rh factor. This usually does not affect the first pregnancy. 

However, subsequent pregnancies are in danger because the antibodies from the first fetus stay in the birthing parent’s blood. The antibodies can enter the fetus’s bloodstream through the placenta and attack the baby’s red blood cells. This leads to anemia and other serious complications. 

The symptoms of erythroblastosis fetalis are caused by the quick destruction of red blood cells in the fetus’s blood. Red blood cells usually last in the body for about 120 days. When the pregnant person’s antibodies attack the fetus’s red blood cells, those cells are destroyed right away.


Erythroblastosis fetalis can be diagnosed with a prenatal ultrasound based on the signs and symptoms present in the fetus. Treatment is started immediately if at least two collections of fluid, known as hydrops, are found in the baby’s tissues. 

Ideally, erythroblastosis fetalis is prevented because of a standard prenatal blood test. It is recommended that all pregnant person be tested for Rh factor through a blood test. This test can determine your Rh factors and if Rh antibodies are present. 

The most common way to determine fetomaternal hemorrhage is the Kleihauer-Betke test. This is an acid elution test in which the newborn's red blood cells react differently in an acidic environment than adult red blood cells.

Another less common test is the fetal-maternal erythrocyte distribution test, which determines the presence of fetal hemoglobin in the mother's blood through flow cytometry. There is no special preparation or fasting needed. 


When erythroblastosis fetalis is caught early, treatment is very effective. The pregnant person is advised to begin RhoGAM shots. RhoGAM is an injection of the Rh immune globulin. This treatment keeps the mother’s body from creating Rh antibodies. 

The dose of RhoGAM depends on the results from the Kleihauer-Betke test or the fetal-maternal erythrocyte distribution test. When there is a small number of fetal red blood cells in the pregnant person’s blood, the standard dose of RhoGAM is given. When there is a high number of fetal red blood cells in the pregnant person’s blood, the RhoGAM dosage must increase to meet the need. 

When the pregnant person is Rh-negative, RhoGAM is usually given at 28 weeks of pregnancy or 72 hours after birth if Rh incompatibility is discovered later. 

It’s important to note that RhoGAM shots will not be effective if the pregnant person’s body has already begun making Rh antibodies. When this occurs, the baby may need several different treatments, depending on their symptoms. 

Treatment for infants with erythroblastosis fetalis may include:


Complications of erythroblastosis fetalis can be prevented in a baby when the birthing parent receives treatment during pregnancy. RhoGAM injections are effective at preventing the production of Rh antibodies that lead to fetal anemia.

When erythroblastosis fetalis is not prevented with prenatal treatment, the condition can quickly become serious and even fatal. This type of anemia causes a baby’s heart to have to work harder to supply oxygen to the body. 

Fortunately, most cases of erythroblastosis fetalis are mild. However, possible complications may include:

  • Anemia 
  • Jaundice 
  • Heart failure
  • Brain damage 
  • Respiratory failure 
  • Stillbirth 
  • Infant death 


The most important way to prevent erythroblastosis fetalis is to have access to quality prenatal care. Rh typing of the mother and father and other testing, as necessary, is recommended to prevent this condition. Having access to this test and to RhoGAM injections, if needed, is effective at preventing the complications of erythroblastosis fetalis.

If you are unsure of your Rh status, talk with your healthcare provider. If you do not have a healthcare provider monitoring your pregnancy, check with the Department of Health and Human Services for free and low-cost resources. 


Erythroblastosis fetalis is an anemia that occurs in a fetus when the pregnant person and the baby have a blood group incompatibility. Rh factor is a protein commonly found on the surface of the red blood cells. When a pregnant person is Rh-negative and the fetus is Rh-positive, the parent's immune system will create Rh antibodies. These antibodies attack the baby’s red blood cells and lead to serious complications. Rh incompatibility can be detected with a standard prenatal blood test, determining if a pregnant person needs Rh immunoglobulin treatment called RhoGAM.

A Word From Verywell

Erythroblastosis fetalis is a serious type of anemia in fetuses and newborns. Any pregnancy complication is scary for parents. To protect yourself and your baby, seek prenatal care as soon as you learn that you are pregnant. Consult your insurance company or state health department for resources if you do not have a prenatal healthcare provider. The earlier you begin prenatal care, the safer you and your baby are. 

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. MedlinePlus. Erythroblastosis fetalis.

  2. MedlinePlus. Hemolytic disease of the newborn.

  3. Children’s Hospital of Wisconsin. Hydrops fetalis/erythroblastosis fetalis.

  4. Science Direct. Kleihauer-betke test.

  5. MedlinePlus. Fetal-maternal erythrocyte distribution blood test.

  6. March of Dimes. Rh disease.

By Carrie Madormo, RN, MPH
Carrie Madormo, RN, MPH, is a health writer with over a decade of experience working as a registered nurse. She has practiced in a variety of settings including pediatrics, oncology, chronic pain, and public health.