Once a mysterious cause of bleeding and bruising in seemingly healthy newborns, fetal and neonatal alloimmune thrombocytopenia (FNAIT) is now recognized as a rare but serious condition—one that researchers learn more about with each decade that passes.
Cases of seemingly healthy newborns with unexplained bleeding, bruising or brain hemorrhages were first described in the 1950s and 1960s, and the symptoms were linked with low blood platelet levels.
It wasn’t until the 1980s that platelet antigen incompatibility was discovered, and the condition was referred to as neonatal alloimmune thrombocytopenia (NAIT). The term “fetal” was added to the diagnosis as a result of advances in prenatal imaging and fetal monitoring in the early 2000s.
What is FNAIT?
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare but serious condition that affects 0.1% of pregnancies in which a pregnant mother’s immune system produces antibodies against the platelets of her fetus. This occurs when a fetus inherits platelet antigens from the father that are not compatible with the mother, typically involving a protein called human platelet antigen (HPA). The mother’s immune system recognizes the fetal platelets as foreign, attacking and destroying them, leading to low platelet levels (thrombocytopenia) in the fetus or newborn.
Exploring comparisons between HDFN and FNAIT
Hemolytic disease of the fetus and newborn (HDFN), which occurs as a result of a blood incompatibility between mother and baby, was identified before FNAIT. At the time, knowledge of HDFN was already more advanced and helped researchers in their approach to understanding FNAIT.
Comparisons were initially made between cases of HDFN and NAIT due to similarities in their clinical presentation. In HDFN, an immune response causes maternal antibodies to develop and attack the fetus’s red blood cells, and in FNAIT, maternal antibodies attack the fetus’s blood platelets.
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Timeline of understanding FNAIT
Since the first clinical descriptions of FNAIT, much progress has been made in the diagnosis and treatment of thrombocytopenia in the fetus and newborn. This has increased awareness around this rare disease, leading to greater understanding of the disease and improved outcomes.
1950s-1960s: First reports of newborns with low blood platelet levels and symptoms of bleeding, bruising and brain hemorrhages.
1970s-1980s: Advances in immunohematology led to the understanding that the mother developed antibodies to her baby’s platelet antigens
1980s-1990s: First use of IVIG in FNAIT-affected pregnancies.
1990s-2000s: Advances in non-invasive fetal diagnostic testing and platelet transfusions, and the use of ultrasound fetal monitoring to detect FNAIT during pregnancy.
2010s – present: Standard use of intravenous immunoglobulin (IVIG) during pregnancy to avoid severe thrombocytopenia, understanding of effect on future pregnancies with use of IVIG for prevention and clinical trials in progress on blocking maternal antibodies.
Unfortunately, there is still no standard prenatal screening program for FNAIT, and infants are often diagnosed post-delivery. However, the prognosis for newborns with FNAIT has significantly improved due to greater recognition of symptoms, allowing for more timely platelet transfusions.
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