Fetal and neonatal alloimmune thrombocytopenia (FNAIT) and hemolytic disease of the fetus and newborn (HDFN) are both rare blood disorders that can occur during pregnancy. They occur as a result of an incompatibility – Rh in HDFN and platelet antigen in FNAIT – between the mother and the baby. The mother’s immune system attacks her baby’s blood. Early detection and treatment are essential for the best outcomes for the baby.
What is HDFN?
Hemolytic disease of the fetus and newborn (HDFN) is an immune-mediated red blood cell 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. Most cases of HDFN are mild and can be treated quickly through an intrauterine transfusion before birth or phototherapy after delivery.
Learn more about HDFN causes and risk factors
What is FNAIT?
FNAIT is often described as the platelet equivalent of HDFN, because in FNAIT, the mother’s immune system attacks fetal platelets. This platelet antigen incompatibility is the result of an antigen inherited from the father, which the mother doesn’t have.
The progressive destruction of fetal platelets leads to thrombocytopenia–a low platelet count–which causes the blood to not clot as it should. There is no standard screening program for FNAIT, so it is often discovered at birth when the newborn has a low platelet count, shows bruising or more seriously, a hemorrhage on the brain.
In cases where a brain hemorrhage has not occurred, treatment by blood transfusion is effective and, in most cases, prevents long-term consequences. Brain hemorrhages can cause permanent brain damage.
FNAIT vs HDFN
FNAIT and HDFN are both rare blood disorders with potentially serious consequences for the fetus and newborn. Prenatal screening will identify the risk for HDFN, with close monitoring during pregnancy and post-delivery important to protect the health of the baby. While the risk factor is known in HDFN, in both conditions, diagnosis is made via maternal blood tests – for anti-HPA antibodies in FNAIT and for antibodies against red blood cells in HDFN.
There are certain similarities and differences to keep in mind when comparing FNAIT and HDFN.
Similarities
Both HDFN and FNAIT are:
- Rare blood disorders in which the mother produces antibodies to attack her baby’s blood.
- Disorders can be diagnosed during pregnancy or post-delivery.
- Diagnosed via blood tests and ultrasound.
- Treated via blood transfusion and intravenous immunoglobulin (IVIG) during pregnancy.
- Aided by early diagnosis and medical intervention.
- Commonly occur in subsequent pregnancies.
- Able to cause severe long-term consequences for the baby, including death, if not treated promptly.
Differences
The differences between HDFN and FNAIT include:
- HDFN is part of standard prenatal screening programs; FNAIT is only screened for if there is a medical or family history.
- FNAIT affects the blood platelets; HDFN affects the red blood cells.
- HDFN rarely affects first pregnancies, whereas in FNAIT it can occur more frequently.
- FNAIT causes bleeding; HDFN causes anemia.
- In the newborn, treatment for FNAIT requires immediate blood transfusion; for HDFN, phototherapy is the primary treatment, followed by blood transfusion if necessary.
