There is no standard prenatal screening program for fetal and neonatal alloimmune thrombocytopenia (FNAIT). This means that unless bleeding is detected on an ultrasound during pregnancy or if the newborn presents with clear FNAIT symptoms, the diagnosis can be missed.
Silent FNAIT refers to mild cases that are asymptomatic, except for a low platelet count, which doctors may attribute to other causes. This is most common in a woman’s first pregnancy. If you suspect FNAIT in your baby, it is important to push for diagnostic tests for the safety of future pregnancies.
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 can silent FNAIT occur?
In FNAIT, maternal antibodies attack the fetus’ blood platelets, causing them to progressively break down. The severity of FNAIT depends on the strength of the maternal antibodies and how long the fetus is exposed to the maternal antibodies during pregnancy. FNAIT is most often diagnosed post-delivery, and cases can vary from mild to moderate to severe.
Learn more about FNAIT testing and diagnosis
Without proper investigation, mild symptoms of FNAIT can be dismissed as non-serious or attributed to other causes.
For example, pinprick bruising (petechiae) and skin discoloration (purpura) can be dismissed as birth trauma. Fussiness and lethargy can be attributed to prematurity, a difficult or long birth experience and jaundice.
If you observe these symptoms in your newborn, ask your healthcare team or the hospital staff to check your baby’s blood platelet count. Without treatment, FNAIT can worsen and lead to long-term neurological damage or even death.
FNAIT is more easily identifiable when other more serious symptoms such as unstemmed bleeding occurs. This can be evident by blood in the urine or stool, hematomas or cephalohematoma and indicates that the blood is not clotting. An urgent platelet transfusion will be required.
The importance of having a clear FNAIT diagnosis
There are two main reasons why obtaining a FNAIT diagnosis is important.
If FNAIT is suspected in the newborn and blood platelet levels are low, treatment will be initiated to boost the platelet count, promote blood clotting and relieve symptoms. A diagnosis of FNAIT can take from 2-6 weeks and the diagnosis will be confirmed well after the need for urgent treatment has passed. But it is important to confirm it, to understand the context of the baby’s health emergency.
A confirmed FNAIT diagnosis is important information for future pregnancies as the maternal antibodies stay in the mother’s system. It can inform prenatal care and allow for proactive measures to help avoid the onset of severe thrombocytopenia in the fetus. Subsequent FNAIT pregnancies can be more severe than the first-affected pregnancy and being informed of the risk is essential.
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