Hemolytic disease of the fetus and newborn (HDFN) can occur in first pregnancies, but it is more often found in pregnancies after the first as a result of antibodies made in a previous pregnancy.
If the Rh-negative mother comes into contact with her Rh-positive baby’s blood at any time, she becomes Rh-alloimmunized. Antibody screening is part of prenatal care, and it can indicate if the pregnant mother has antibodies to Rh-positive blood types in subsequent pregnancies.
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 (Rh) factor (Rh-positive or Rh-negative) during pregnancy. Numerous antibodies to RBC antigens can be linked to HDFN, such as those from the ABO and Rh blood group systems.
How can future pregnancies be affected by HDFN?
Even if the first pregnancy was unaffected, the risk of HDFN is higher in pregnancies following the first. It is possible for a mother to be accidentally exposed to the blood of her first Rh-positive baby during a medical intervention, miscarriage, trauma or delivery.
Learn more about HDFN causes and risk factors
If this takes place, the mother’s immune system may react by producing anti-D antibodies against the baby’s red blood cells. The mother is now Rh-sensitized, and these antibodies can stay in her system for a number of years. In a subsequent Rh-positive pregnancy, they become reactivated. The antibodies then cross the placenta and attack the red blood cells of the fetus, breaking them down and leading to fetal anemia.
Screening for anti-D antibodies
Early in pregnancy, a prenatal antibody screening assessment will determine whether a mother has anti-D antibodies and indicate the risk of the fetus developing HDFN. If antibodies are present, a multidisciplinary medical team, which often includes a maternal-fetal specialist, will monitor the pregnancy and the health of the fetus will be under close observation through regular ultrasounds and blood tests.
Treating HDFN in utero
If HDFN develops, intrauterine transfusions (IUT) may be needed to treat fetal anemia and prevent it from developing into hydrops fetalis, which causes extensive swelling.
What is hydrops fetalis?
Hydrops fetalis is a symptom of an underlying medical condition that affects an unborn baby and can occur with HDFN. In this condition, large amounts of fluid accumulate in the baby’s tissues or organs. If it remains untreated, this abundance of fluid can place stress on the fetal heart and other vital organs, thus causing the life of the fetus to be at risk.
It may be necessary to measure the fetal hemoglobin level every two weeks, and an early delivery is likely. In the most severe cases, the fetus can suffer from cardiac arrest and even stillbirth, though this is rare and can often be prevented through early treatment.
Severity of HDFN in later pregnancies
In later pregnancies, HDFN is often reported as being more severe than in first pregnancies, with risks rising with each subsequent pregnancy. This may be due to the fact that the antibodies are already present and can attack the fetus’s red blood cells earlier.
However, when antibodies are detected early in pregnancy and HDFN is diagnosed and then treated immediately, the disease is often less severe. This leads to better outcomes for the baby, emphasizing the importance of early testing and treatment.
