Why a late FNAIT diagnosis is still important even years after birth

For women with a history of fetal and neonatal alloimmune thrombocytopenia (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.), the risk of the condition affecting a subsequent pregnancy is higher. If the previous child had severe symptoms, the probability of recurrence in a subsequent pregnancy is around 70%. 

However, prophylaxis with intravenous immunoglobulinIntravenous immunoglobulin A treatment given to pregnant women with a history of FNAIT or known alloantibodies. IVIG reduces the immune reaction against fetal platelets. (IVIGIntravenous immunoglobulin A treatment given to pregnant women with a history of FNAIT or known alloantibodies. IVIG reduces the immune reaction against fetal platelets.) is available and can be used to reduce the risk of severe complications, particularly 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.  (ICH). This is why identifying FNAIT even years after an affected child was born can provide important information for future pregnancies.

FNAIT may be missed at birth

Although laboratory tests can identify HPAHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT. incompatibility and maternal anti-HPA antibodies when investigating a possible FNAIT diagnosis, they are not currently used for routine population screening. One reason is that a positive result does not reliably predict how severely the fetus will be affected, making it difficult to determine which pregnancies would benefit from preventive treatment.

FNAIT can present with mild symptoms or even be asymptomatic, and some cases can go unnoticed. The disease does not always cause obvious signs such as bleeding, particularly in milder cases.

Some cases are only identified because the infant undergoes blood tests for other reasons. Even after finding a 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. (thrombocytopeniaThrombocytopenia A platelet count that is lower than normal.) in the blood tests, clinicians would have to suspect the disease and order specific testing. As there are many other possible causes of thrombocytopenia, if the suspicion does not cross the doctor’s mind, the condition can go unnoticed.

In one study of women diagnosed with FNAIT in a subsequent pregnancy, four of 26 had not been appropriately tested for the condition after an earlier baby developed findings such as thrombocytopenia or ICH.

Read more about FNAIT testing and diagnosis

How a previous diagnosis can guide future pregnancies

Patients with a history of FNAIT require special care when planning future pregnancies. Here are some steps to consider when planning to have another child:

• Tell your obstetrician about the previous FNAIT diagnosis. Even if the affected child was born years ago, the previous diagnosis changes how a future pregnancy is monitored.
• Carry records from the previous pregnancy and birth. Old platelet counts, discharge summaries, imaging results and any previous antibody or HPA test results can help the care team assess the risk.
• Ask if you need specialist care. Women with a previous FNAIT pregnancy should be referred to maternal-fetal medicine, hematology or a center experienced in FNAIT.
• Discuss testing early in pregnancy. Depending on what is already known, testing may be used to confirm the maternal antibody, HPA incompatibility and whether the fetus carries the relevant antigen.
• Ask about preventive treatment. IVIG treatment can be recommended during pregnancy, especially if a previous child had a severe presentation such as ICH.
• Make a delivery and newborn care plan. The care team can prepare for platelet testing and treatment after birth in case it is needed.

Long-term effects of FNAIT

Some children may experience long-term effects from complications associated with FNAIT. A 2023 study evaluated 44 children with FNAIT at a median age of 12 years and found that 7% had severe neurodevelopmental impairment and 25% had mild-to-moderate neurodevelopmental impairment. 

Neurodevelopmental issues were also found in some children without diagnosed intracranial hemorrhage (ICH). A study published in 2019, which evaluated sequelae in children who presented with ICH, found that 60% had severe neurodevelopmental impairment.

For a child with unexplained neurodevelopmental problems and a history of thrombocytopenia or other complications around birth, a late FNAIT diagnosis may help explain the origin of these problems and provide important context for their medical history.