Hemolytic Disease of the Newborn (HDN)

What is Hemolytic Disease of the Newborn (HDN)?

Hemolytic disease of the newborn is a blood disorder that affects babies before or shortly after birth. It happens when the mother's immune system produces antibodies that attack and destroy the baby's red blood cells. This condition is also called erythroblastosis fetalis.

The most common cause is Rh incompatibility. If a mother has Rh-negative blood and her baby has Rh-positive blood, her body may see the baby's blood cells as foreign invaders. The mother's immune system then makes antibodies that cross the placenta and break down the baby's red blood cells. This leads to anemia, a condition where the baby doesn't have enough healthy red blood cells to carry oxygen.

HDN can also occur due to ABO blood type incompatibility or other rare blood group differences. When red blood cells break down too quickly, a yellow pigment called bilirubin builds up in the baby's blood. High bilirubin levels can cause jaundice and, in severe cases, brain damage if left untreated. Fortunately, screening during pregnancy can identify women at risk so doctors can monitor and prevent complications.

Bilirubin, Total

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Rh Typing

Determine your baby's Rh compatibility
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Symptoms

Jaundice, a yellowing of the skin and eyes that appears within 24 hours of birth
Pale skin due to anemia
Enlarged liver or spleen that a doctor can feel during examination
Swelling or fluid buildup in the baby's body, called hydrops fetalis
Rapid heart rate or breathing difficulties
Listlessness or poor feeding
Low muscle tone

Some babies with mild HDN may show no symptoms at birth. However, jaundice often appears within the first 24 to 48 hours of life as bilirubin levels rise. Severe cases can cause serious complications if not detected and treated promptly.

Causes and risk factors

HDN is caused by blood type incompatibility between mother and baby. The most common trigger is Rh incompatibility. When an Rh-negative mother carries an Rh-positive baby, she may develop antibodies during pregnancy or childbirth. These antibodies typically form after the mother's blood comes into contact with the baby's blood, which can happen during delivery, miscarriage, amniocentesis, or abdominal trauma. First pregnancies rarely cause problems because the mother hasn't been sensitized yet. But in future pregnancies with Rh-positive babies, those antibodies can cross the placenta and attack the baby's red blood cells.

ABO incompatibility is another cause, occurring when a mother with type O blood carries a baby with type A, B, or AB blood. This form is usually milder than Rh incompatibility. Risk factors include previous pregnancies, miscarriages, or blood transfusions that may have sensitized the mother's immune system. Women who didn't receive Rh immunoglobulin injections during previous pregnancies are at higher risk. Rare blood group incompatibilities involving Kell, Duffy, or other antigens can also trigger HDN in some cases.

How it's diagnosed

HDN is diagnosed through blood tests performed during pregnancy and after birth. Pregnant women receive routine blood typing and an antibody screen to check their ABO group, Rh type, and whether they have developed antibodies against fetal blood cells. If a mother is Rh-negative and the father is Rh-positive, doctors monitor antibody levels throughout pregnancy. After birth, doctors test the baby's blood for bilirubin levels, blood type, Rh factor, and signs of red blood cell breakdown.

Rite Aid offers testing for the key markers involved in HDN screening, including ABO group, Rh type, antibody screen, and total bilirubin. Early detection through blood testing allows doctors to monitor at-risk pregnancies and provide preventive treatment. Testing at Quest Diagnostics locations makes screening accessible and convenient for expectant mothers.

Treatment options

Rh immunoglobulin injections given to Rh-negative mothers around week 28 of pregnancy and within 72 hours after delivery to prevent antibody formation
Phototherapy using special blue lights to break down excess bilirubin in newborns with jaundice
Intravenous immunoglobulin to reduce antibody activity in affected babies
Exchange transfusion to replace the baby's blood with donor blood in severe cases
Intrauterine blood transfusions for babies with severe anemia before birth
Close monitoring of bilirubin levels in the days following birth
Ensuring adequate feeding and hydration to help the baby's body eliminate bilirubin
Early delivery may be recommended if the baby shows signs of severe distress

Frequently asked questions

The main cause is Rh incompatibility between mother and baby. When an Rh-negative mother carries an Rh-positive baby, her immune system can produce antibodies that attack the baby's red blood cells. This typically happens in second or later pregnancies after the mother has been sensitized. ABO blood type incompatibility can also cause HDN but is usually less severe.

Yes, Rh-related HDN can often be prevented with Rh immunoglobulin injections. These shots are given to Rh-negative mothers around week 28 of pregnancy and within 72 hours after delivery. The injection prevents the mother's immune system from forming antibodies against the baby's Rh-positive blood. Preventive treatment has dramatically reduced severe cases of HDN.

Pregnant women receive routine blood tests to check their blood type, Rh factor, and antibody levels. If a mother is Rh-negative, doctors monitor her antibody screen throughout pregnancy to see if she's developing antibodies. Ultrasounds may also check for signs of anemia or fluid buildup in the baby. These screening tests help identify at-risk pregnancies early.

Babies with HDN may develop jaundice, anemia, or more serious complications depending on severity. Mild cases often require only phototherapy to treat jaundice. Moderate to severe cases may need intravenous immunoglobulin or exchange transfusions. With prompt treatment, most babies recover fully without long-term effects.

HDN is rarely a problem in first pregnancies because the mother hasn't been sensitized to the baby's blood type yet. Sensitization usually occurs during delivery when maternal and fetal blood mix. Later pregnancies with Rh-positive babies are at higher risk because the mother already has antibodies. This is why preventive Rh immunoglobulin is so important after each pregnancy.

Bilirubin is a yellow pigment created when red blood cells break down. In HDN, the baby's red blood cells are destroyed faster than normal, causing bilirubin to build up. High bilirubin levels cause jaundice and can damage the brain if untreated. Doctors monitor bilirubin levels closely in babies at risk for HDN.

Yes, ABO incompatibility can cause HDN, though it's usually milder than Rh disease. This occurs most often when a mother has type O blood and her baby has type A or B blood. The mother's natural antibodies against A or B antigens can cross the placenta. Most cases are mild and respond well to phototherapy.

Key screening tests include blood typing to determine ABO group and Rh type, plus an antibody screen to check for antibodies against fetal red blood cells. Pregnant women typically get these tests at their first prenatal visit. If antibodies are detected, doctors may order antigen typing and monitor antibody levels throughout pregnancy.

Severe HDN diagnosed before birth may require intrauterine blood transfusions. A doctor uses ultrasound guidance to deliver blood to the baby through the umbilical cord. This treats severe anemia and can keep the baby healthy until delivery. In some cases, early delivery may be planned if the baby is mature enough.

If you're Rh-negative and your baby is Rh-positive, doctors will monitor your baby's bilirubin levels and watch for signs of jaundice or anemia. Most babies do fine with routine monitoring. If jaundice develops, phototherapy usually resolves it quickly. Your baby may need blood tests in the first few days to check bilirubin and red blood cell counts.