Pregnancies affected by fetal and neonatal alloimmune thrombocytopenia (FNAIT) 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 hemorrhage.
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 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 count 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 immunoglobulin (IVIG) 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 hemorrhage (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 unit (NICU). 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 transfusion, 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.
