Pregnancies affected by 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.) often culminate in a premature birth.
Early delivery can be necessary by cesarean to remove the fetus from the toxic effects of the maternal anti-platelet antigen antibodies and to provide urgent treatment to the fetus in the case of complications, such as bleeding or hemorrhageFetal hemorrhage Any bleeding that occurs before birth. In FNAIT, this usually results from extremely low platelet counts..
What is FNAIT?
Fetal and neonatal alloimmune thrombocytopeniaFetal 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. (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 antigenHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT. (HPAHuman platelet antigen Proteins found on the surface of platelets. Incompatibility between maternal and fetal human platelet antigens can trigger FNAIT.). The mother’s immune system recognizes the fetal platelets as foreign, attacking and destroying them, leading to low platelet levels (thrombocytopeniaThrombocytopenia A platelet count that is lower than normal.) in the fetus or newborn.
FNAIT and pregnancy
There is no standard screening procedure for FNAIT, so it often goes undetected unless a woman has a family history of FNAIT or previous FNAIT-affected pregnancies or if bleeding is identified. When the fetus’s blood platelets are attacked by maternal antibodies, it dramatically reduces the baby’s 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. and stops the blood from clotting.
When FNAIT is diagnosed during pregnancy, treatment is available to protect the fetus in utero and help prevent a dangerously early delivery. 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 administered to the mother, with or without corticosteroids, to help improve the fetus’s immune response and blood platelet count. This reduces the risk of bleeding and hemorrhage, including 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), which can be life threatening or result in lifelong neurological damage.
Premature birth and FNAIT
Pregnancies affected by FNAIT are considered high-risk and are therefore closely monitored. An elective cesarean two to four weeks before term is commonly advised in women who have experienced previous FNAIT-affected pregnancies or when the fetus is at high risk. Vaginal delivery is still possible in lower risk cases of FNAIT, with no increased risk of ICH being linked to vaginal birth.
In cases of fetal distress or lack of fetal movements, an emergency cesarean may be required. Premature delivery and lower birth weight have been found to occur more frequently in FNAIT-affected pregnancies.
Postnatal care
Most premature babies require care in the neonatal intensive care unitNeonatal intensive care unit A specialized hospital unit for newborns who need close monitoring and treatments such as platelet transfusions. (NICUNeonatal intensive care unit A specialized hospital unit for newborns who need close monitoring and treatments such as platelet transfusions.). As soon as the baby is delivered, he or she will be assessed for signs of a pinpoint rash, bruising, bleeding or hemorrhage. These are key indicators for thrombocytopenia, or a very low blood platelet count.
Before waiting for the platelet count to be tested by a blood sample, immediate intervention is necessary to prevent severe complications such as ICH and other potential hemorrhages in internal organs, such as the spine and stomach. The first-line treatment is a platelet transfusionPlatelet transfusion A treatment for newborns with very low platelet counts that ideally uses HPA-compatible or washed maternal platelets., with the option of follow up treatment of intravenous immunoglobin. An ultrasound or MRI will confirm and monitor ICH.
Throughout treatment, the newborn’s platelet count needs to be measured and monitored to ensure the count is rising. If no ICH occurs, thrombocytopenia usually resolves in two to six weeks.
