Pregnancies affected by fetal and neonatal alloimmune thrombocytopenia (FNAIT) may have an increased risk of miscarriage as a result of severe fetal thrombocytopenia and associated complications.
Early diagnosis, non-invasive testing, close monitoring and proactive treatment in FNAIT-affected pregnancies can all contribute to better outcomes and a lower risk of miscarriage.
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 FNAIT cause miscarriage?
There is no prenatal screening program for FNAIT, so in first pregnancies affected by FNAIT, most cases go undetected during pregnancy. FNAIT is often only identified following delivery when newborns present with symptoms such as a low platelet count, bruising, red or purple skin discoloration called purpura and petechiae and hematomas.
During pregnancy, if the fetus experiences a very low platelet count, this stops the blood from clotting. As a result, the fetus can suffer from uncontrollable bleeding and hemorrhage in the brain, gastrointestinal tract, eyes and lungs. If undetected and left untreated, complications of FNAIT can be life-threatening for the fetus. In particular, intracranial hemorrhage can cause long-term neurological damage or fetal death.
How to reduce the risk of miscarriage in FNAIT?
If previous pregnancies have been affected by FNAIT or if there is a family history of FNAIT pregnancies, monitoring and proactive medical treatment is standard. The onset of FNAIT during pregnancy can be overlooked if it occurs unexpectedly.
Early diagnosis: FNAIT may be suspected if the fetus has a low fetal platelet count or hemorrhages are detected by ultrasound.
Close monitoring: FNAIT-affected pregnancies require regular monitoring by ultrasound to check for bleeding or hemorrhaging.
Non-invasive treatment: A low fetal blood platelet count prevents the blood from clotting correctly. This means that any invasive test such as chorionic villus sampling or amniocentesis, which is used for fetal genotyping may lead to bleeding or hemorrhage, and potentially miscarriage. However, a non-invasive cell-free DNA test can also be used in fetal genotyping, with a lower risk for the fetus.
Medical intervention: The administration of intravenous immunoglobulin (IVIG) and corticosteroids during pregnancies at risk of FNAIT or affected by FNAIT is effective in delaying the onset of severe fetal thrombocytopenia and the occurrence of intracranial hemorrhage (ICH). These treatments suppress the maternal antibodies that attack and destroy the fetus’s blood platelets, delaying or preventing the risk of complications and fetal death related to a low blood platelet count.
Early delivery: The decision to deliver the baby early by cesarean may be taken if the fetus is in distress or FNAIT symptoms, such as ICH, require urgent treatment.
