Glossary

An antibody a pregnant woman develops in response to fetal platelets that carry a different human platelet antigenHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT.. These antibodies can cross the placenta and destroy fetal platelets.

The process by which the mother becomes sensitized to fetal platelet antigens and begins producing alloantibodies. This is what causes FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth..

Bleeding inside the fetal brain, also known as an intracranial hemorrhageBrain bleed Bleeding inside the fetal brain, also known as an intracranial hemorrhage. In FNAIT, it's often caused by severe thrombocytopenia and can lead to long-term disability or death. . In FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth., it’s often caused by severe thrombocytopeniaSevere thrombocytopenia A dangerously low platelet count, typically below 50,000 platelets per microliter and sometimes far lower in FNAIT. and can lead to long-term disability or death. 

A procedure in which fetal blood is drawn from the umbilical cord to check platelet levels. It carries risks and is not used often today to treat FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth..

Coordinating when, where and how an FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth.-affected baby will be delivered to ensure access to specialists, platelet transfusionPlatelet transfusion A treatment for newborns with very low platelet counts that ideally uses HPA-compatible or washed maternal platelets. support and a neonatal intensive care unitNeonatal intensive care unit A specialized hospital unit for newborns who need close monitoring and treatments such as platelet transfusions..

A specialized transport protein. In FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth., it carries maternal antiplatelet IgG antibodies across the placenta into the fetus, which destroys the fetus’s platelets.

A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth.

Any bleeding that occurs before birth. In FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth., this usually results from extremely low platelet counts.

Can include Ultrasounds, Doppler studies and other evaluations that help the care team track fetal health and watch for potential complications.

A laboratory test that identifies which platelet antigens a person carries. Often used to confirm HPAHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT. incompatibility and assess recurrence riskRecurrence risk The chance that FNAIT will affect future pregnancies. Once a woman is sensitized, the risk of FNAIT in future pregnancies is high..

The most common cause of FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth., this occurs when there is a genetic mismatch between a pregnant mother, who is HPAHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT.-1a negative, and her baby, who has inherited the HPA-1a positive antigen from the father.

Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth..

Low platelet countPlatelet count A measure of how many platelets are in the blood. FNAIT is characterized by severely reduced counts in a fetus or newborn. caused by the immune system attacking platelets. FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth. is a type of immune-mediated thrombocytopeniaImmune-mediated thrombocytopenia Low platelet count caused by the immune system attacking platelets. FNAIT is a type of immune-mediated thrombocytopenia..

A treatment given to pregnant women with a history of FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth. or known alloantibodies. IVIGIntravenous immunoglobulin A treatment given to pregnant women with a history of FNAIT or known alloantibodies. IVIG reduces the immune reaction against fetal platelets. reduces the immune reaction against fetal platelets.

A doctor who manages high-risk pregnancies, including those affected by FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth..

A specialized hospital unit for newborns who need close monitoring and treatments such as platelet transfusions.

Low platelet countPlatelet count A measure of how many platelets are in the blood. FNAIT is characterized by severely reduced counts in a fetus or newborn. in a newborn. In FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth., platelet levels may drop dangerously low within hours after birth.

Testing the father’s blood to determine which HPAs may have been passed to the fetus.

The process by which the placenta uses the neonatal Fc receptorFc receptor A specialized transport protein. In FNAIT, it carries maternal antiplatelet IgG antibodies across the placenta into the fetus, which destroys the fetus's platelets. (FcRnFc receptor A specialized transport protein. In FNAIT, it carries maternal antiplatelet IgG antibodies across the placenta into the fetus, which destroys the fetus's platelets.) to transfer maternal IgG antibodies to provide the fetus with passive immunity. In FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth., this process misroutes harmful anti-platelet alloantibodies into the fetal circulation.

Testing that identifies specific HPAs on maternal or paternal platelets to determine the risk of incompatibility.

A measure of how many platelets are in the blood. FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth. is characterized by severely reduced counts in a fetus or newborn.

A treatment for newborns with very low platelet counts that ideally uses HPAHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT.-compatible or washed maternal plateletsWashed maternal platelets Platelets collected from the mother and washed to remove plasma. Often used for transfusion in newborns when matched donor platelets are unavailable..

The chance that FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth. will affect future pregnancies. Once a woman is sensitized, the risk of FNAIT in future pregnancies is high.

Specially matched donor platelets, often HPAHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT.-negative, used for transfusions in newborns with FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth..

Another term for alloimmunizationAlloimmunization The process by which the mother becomes sensitized to fetal platelet antigens and begins producing alloantibodies. This is what causes FNAIT., this refers to the immune system’s response to foreign platelet antigens.

A dangerously low platelet countPlatelet count A measure of how many platelets are in the blood. FNAIT is characterized by severely reduced counts in a fetus or newborn., typically below 50,000 platelets per microliter and sometimes far lower in FNAITFetal and neonatal alloimmune thrombocytopenia A rare condition in which a mother’s immune system attacks fetal platelets, leading to dangerously low platelet levels before and/or after birth..

A platelet countPlatelet count A measure of how many platelets are in the blood. FNAIT is characterized by severely reduced counts in a fetus or newborn. that is lower than normal.

Platelets collected from the mother and washed to remove plasma. Often used for transfusion in newborns when matched donor platelets are unavailable.