The recurrence rate of fetal and neonatal alloimmune thrombocytopenia (FNAIT) in subsequent pregnancies is up to 90%. However, siblings may experience FNAIT differently, with varying degrees of severity based on their place in the birth order, antibody levels, treatment timing, and effectiveness.
Preparing for a new pregnancy following an experience with FNAIT requires careful planning, close monitoring, and preventative care to provide the best care for the baby.
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.
FNAIT in subsequent pregnancies
When a mother develops antibodies to her fetus’s blood platelets, her body keeps the antibodies for life. This means that any subsequent pregnancies are at a high risk of being affected by FNAIT.
A confirmed diagnosis of FNAIT in a newborn informs the way future pregnancies are managed, with stricter prenatal testing and close monitoring throughout pregnancy.
For women affected by FNAIT, it occurs in first pregnancies in almost 50% of cases. Often, the initial FNAIT-affected pregnancy involves only mild to moderate symptoms, as it takes time for antibodies to be produced and to cross the placenta. The severity of FNAIT may increase with each pregnancy, as the anti-HPA antibodies are already present in the mother and can cross the placenta at an earlier stage.
Learn more about FNAIT signs and symptoms
Siblings with FNAIT
As there is no standard FNAIT prenatal screening program, the first FNAIT-affected pregnancy usually happens without warning. While some cases are identified in utero, often later in pregnancy, FNAIT is most often detected at birth. An FNAIT-affected newborn presents with a combination of symptoms such as a low platelet count, bruising, unexplained bleeding, a pinprick red rash (petechiae) or purple skin discoloration (purpura), fussiness and fatigue. In the first FNAIT pregnancy, if the baby is often only mildly affected or shows no symptoms, the infant may never be diagnosed.
Future pregnancies that share the same father don’t necessarily follow a pattern, and symptoms can vary from mild or moderate to severe, depending on the level of antibodies and how early in the pregnancy they cross the placenta. Preventive treatment can also help delay the onset of FNAIT in at-risk pregnancies.
Preparing for subsequent FNAIT pregnancies
Once an FNAIT-affected pregnancy occurs, later pregnancies are considered to have a high risk of developing FNAIT. To ensure the best outcomes for future siblings, certain precautions are taken, such as:
- Non-invasive testing may be recommended to determine the fetus’s platelet type.
- The pregnant mother’s anti-HPA antibody levels may be measured to help understand the risk to the fetus.
- Intravenous immunoglobulin (IVIG) with or without steroids may be administered starting from 12-16 weeks’ gestation until delivery.
Staying informed and making sure you have support from family and friends can help you manage any stress and anxiety you may feel.
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