Hemolytic Disease

Hemolytic disease of the newborn (HDN) — also called erythroblastosis fetalis — is a blood disorder that occurs when the blood types of a mother and baby are incompatible. HDN is relatively uncommon in the United States due to advances in early detection and treatment, limiting it to approximately 4,000 cases a year. It is more likely to happen during a mother’s second or subsequent pregnancy. There are two causes, Rh incompatibility and ABO incompatibility. HDN due to Rh incompatibility occurs more frequently and is often called Rh disease; it is about three times more likely in Caucasian babies than in African-American babies. HDN can be treated during pregnancy or after the baby is born.

Hemolytic disease of the newborn is very preventable. Today, nearly all women with Rh-negative blood are identified in early pregnancy through blood tests. If a mother is Rh-negative and has not been sensitized, she is usually given a drug called Rh immunoglobulin, or RhoGAM. This specially developed blood product prevents an Rh-negative mother's antibodies from reacting to her baby’s Rh-positive red blood cells. Mothers are typically given RhoGAM around the 28th week of pregnancy and again within 72 hours of giving birth.

Each child may experience different symptoms of hemolytic disease of the newborn (HDN). The most common symptoms of HDN are:

• Pale skin
• Yellowing of the amniotic fluid, umbilical cord, skin, and eyes
• Enlarged liver or spleen
• Severe swelling of the body

During pregnancy, it is possible for symptoms to include:

• Mild anemia: When the baby’s red blood cell count is deficient, his blood cannot carry enough oxygen from the lungs to all parts of his body, causing his organs and tissues to struggle.
• Hyperbilirubinemia and jaundice: The breakdown of red blood cells produces bilirubin, a brownish yellow substance that is difficult for a baby to discharge and can build up in his blood (hyperbilirubinemia) and make his skin appear yellow.
• Severe anemia with enlargement of the liver and spleen: The baby’s body tries to compensate for the breakdown of red blood cells by making more of them very quickly in the liver and spleen, which causes the organs to get bigger. These new red blood cells are often immature and unable to function completely, leading to severe anemia.
• Hydrops fetalis: When the baby’s body cannot cope with the anemia, his heart begins to fail and large amounts of fluid buildup in his tissues and organs.

After birth, possible symptoms include:

• Severe hyperbilirubinemia and jaundice: Excessive buildup of bilirubin in the baby’s blood causes his liver to become enlarged.
• Kernicterus: Buildup of bilirubin in the blood is so high that it spills over into the brain, which can lead to permanent brain damage.

HDN occurs when the blood types of a mother and baby are incompatible. If the baby’s incompatible red blood cells cross over to their mother, through the placenta during pregnancy or at delivery, the immune system sees them as foreign and responds by developing proteins called antibodies to attack and break them down. This can lead to several complications that range from mild to very severe.

The mother’s immune system also keeps these antibodies in case the incompatible red blood cells appear again, making them “sensitized.” Because of this, HDN is more likely to occur during a second or subsequent pregnancy, or following a miscarriage or abortion.

A person’s blood type is determined by the presence of two different types of proteins, called antigens. The A, B, and O antigens represent the classification of a person’s blood as Type A, B, AB, or O. If a person also has the Rh factor antigen, his blood is Rh -positive, and if not, it is Rh-negative.

Hemolytic disease of the newborn can be diagnosed during pregnancy or after the baby is born.

Tests conducted during pregnancy may include:

• Complete blood count test for the mother
• Ultrasound
• Amniocentesis
• Cordocentesis

After birth, tests may include:

• Complete blood count test for the baby
• Umbilical cord blood test

Hemolytic disease of the newborn can be treated during pregnancy or after the baby is born. Treatment during pregnancy may include:

• Blood transfusion
• Early delivery of the baby if severe complications arise and baby's lungs are mature

After birth, treatment may include:

• Blood transfusion
• Intravenous fluids
• Oxygen or mechanical breathing machine
• Exchange transfusion to replace the baby's damaged blood with fresh blood

Hemolytic disease of the newborn (HDN) is treated through the Blood Disorders Center at Dana-Farber/Boston Children's. Hemolytic disease of the newborn was first identified in 1932 at Boston Children’s Hospital by Dr. Louis Diamond. He went on to develop the first successful treatment, a transfusion procedure, in the 1940s.