Regular monitoring of pregnant women at risk of fetal and neonatal alloimmune thrombocytopenia (FNAIT) developing in their baby ensures early identification of this rare blood disease. This allows timely diagnosis and treatment and avoids life-threatening complications in the fetus, such as intracranial hemorrhage (ICH).
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.
How do you know if you are at risk of FNAIT?
There is no standard prenatal screening program for FNAIT. In first pregnancies, the risk for FNAIT is identified based on family medical history, in particular if your sister experienced an FNAIT-affected pregnancy. If your first baby developed FNAIT, there is a high risk of recurrence in subsequent pregnancies, an increased risk of severity and earlier onset, as the maternal antibodies already exist.
When is regular monitoring required?
In first pregnancies, when the risk of FNAIT is identified, regular blood tests are required to detect antibodies, which confirm the alloimmunization of the pregnant woman. When a pregnant woman becomes alloimmunized, her immune system develops antibodies against her baby’s blood platelets. As the fetus’s blood platelets break down and the fetal blood platelet count decreases, the blood loses its ability to clot.
In subsequent pregnancies, counseling, monitoring and risk assessment occur at the start of the pregnancy. Additionally, in pregnancies at high-risk of FNAIT, the administration of intravenous immunoglobulin (IVIG) and corticosteroids helps delay the onset of severe fetal thrombocytopenia and prevent complications.
What does regular monitoring involve?
Monitoring of an FNAIT-affected pregnancy is mostly non-invasive to avoid any risk of bleeding in the fetus and aims to assess the severity of fetal thrombocytopenia and predict the occurrence of hemorrhages.
Blood tests: To monitor the maternal antibody levels and help predict the severity of FNAIT on the fetus.
Ultrasound: Serial ultrasounds check every 2-4 weeks for bleeding and hemorrhage in the fetus’s brain. ICH is the most serious complication of FNAIT, which can potentially lead to long-term neurological damage or fetal death. Early delivery by cesarean starting from 34 weeks may be required to more effectively treat ICH.
Fetal blood sampling: If more invasive methods are considered necessary by the healthcare team, fetal blood sampling can be used to determine the fetal blood count. This involves inserting a needle into the pregnant woman’s abdomen and extracting a small sample of fetal blood. The associated risks include rupture of the membranes, infection, bleeding, contractions, miscarriage and early delivery.
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