Fetuses affected by hemolytic disease of the fetus and newborn (HDFN) are often born prematurely, at a gestational age of less than 37 weeks.
Following treatment by intrauterine transfusionIntrauterine transfusion A procedure that delivers donor red blood cells to the fetus through the umbilical vein to treat severe anemia caused by HDFN. in utero, the pregnancy is prolonged as long as possible to allow sufficient time for the development of the lungs and the hepatic enzyme system. However, the delicate timing of delivery is also important to prevent morbidity and mortality due to anemiaAnemia A condition that occurs when the body doesn’t have enough healthy red blood cells to carry oxygen to its tissues. In HDFN, anemia occurs when maternal antibodies destroy fetal red blood cells. and hydrops fetalisHydrops fetalis A serious, sometimes fatal condition in which fluid builds up in a baby’s tissues and organs due to severe anemia from HDFN. in the fetus.
What is HDFN?
Hemolytic disease of the fetus and newborn (HDFN) is an immune-mediated red blood cell (RBC) disorder that occurs when a baby’s RBCs break down quickly, which is called hemolysis. HDFN is caused by a mismatch between a mother’s and her baby’s blood type (A, B, AB, or O) or Rhesus (RhRh factor A protein or antigen found on red blood cells. When an Rh-negative mother carries an Rh-positive fetus, her immune system may make antibodies that attack the fetus' red blood cells.) factor (Rh-positiveRh-Positive A blood type trait that means your red blood cells have the Rh(D) antigen. or Rh-negativeRh-Negative A blood type trait that means your red blood cells lack the Rh(D) antigen.) during pregnancy. Numerous antibodiesAntibody A protein made by the immune system that recognizes and attacks foreign substances, such as bacteria, or in HDFN, fetal red blood cells carrying incompatible antigens. to RBC antigensAntibody A protein made by the immune system that recognizes and attacks foreign substances, such as bacteria, or in HDFN, fetal red blood cells carrying incompatible antigens. can be linked to HDFN, such as those from the ABO and Rh blood groupBlood group A classification of blood based on inherited markers found on red blood cells. The ABO and Rh blood groups are most common in HDFN. systems.
Risks and challenges for preterm babies with HDFN
Babies born with HDFN face numerous risks and challenges during birth and following delivery. This is particularly true of babies born earlier than 37 weeks gestation whose lungs and liver have not had time to fully develop.
At birth, premature babies may have the following symptoms: very pale skin due to anemia, yellow coloring of the eyes due to jaundiceJaundice A common symptom of HDFN, jaundice is caused by excess bilirubin and is characterized by a yellow tint to the skin or eyes., difficulty in breathing, swelling of the liver or spleen and swelling of the whole body due to hydrops fetalis. These symptoms can also cause the newborn to be irritable and tired, leading to poor feeding.
Acute postnatal management in a neonatal intensive care unit is essential to ensure successful outcomes for a preterm baby with HDFN.
Treatment options for preterm babies with HDFN
In addition to close monitoring of the preterm baby’s condition and blood tests to monitor blood count and bilirubinBilirubin A yellow substance produced when red blood cells break down. High bilirubin levels in newborns with HDFN can cause jaundice or, in severe cases, brain damage. levels, postnatal treatment includes several options. These include oxygen to assist breathing, intravenous fluids if blood pressure is low, intensive phototherapyPhototherapy A treatment that uses special blue light to help newborns break down bilirubin and prevent kernicterus. to treat jaundice, blood transfusions to treat anemia and in severe cases, exchange transfusions.
An exchange transfusion is performed in cases of severe anemia and toxic levels of bilirubin in newborns affected by HDFN. It is an invasive procedure that replaces 60% of the baby’s blood volume.
Preterm babies affected by HDFN often suffer from hyperbilirubinemiaHyperbilirubinemia A common cause of jaundice, this refers to higher than normal bilirubin levels in the blood., causing jaundice or the yellow discoloration of the baby’s eyes and then the skin.
The breakdown of the baby’s red blood cells creates a buildup of bilirubin in the blood. As the preterm newborn’s immature liver struggles to process the excess bilirubin, intensive phototherapy is required to prevent it from reaching toxic levels. If the bilirubin levels become too high, there is a risk that the bilirubin will cross into the brain and lead to kernicterus, a type of brain damage.
Premature babies may need to stay in the hospital until they reach their pregnancy due date. This may be prolonged until they gain body weight, can maintain their body temperature and reach certain milestones. To continue treatment of anemia post-discharge, some babies will require top-up blood transfusions during the first couple of months.
