Often, fetal and neonatal alloimmune thrombocytopenia (FNAIT) is detected only following delivery when babies have a low platelet count or present with unexplained bruising, bleeding or hemorrhages in the brain, spinal cord or stomach.
If FNAIT is diagnosed during pregnancy, treatment can begin to help prevent severe thrombocytopenia or low blood platelet count in the baby. Care must be taken during delivery to minimize the risks of bleeding and hemorrhaging, in particular intracranial hemorrhage (ICH).
If your child is at risk for FNAIT or has been previously diagnosed, there are certain steps you can take to prepare for a smoother labor and delivery.
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 does FNAIT occur?
A pregnant mother can become alloimmunized to the fetal platelet antigens of her baby, that are inherited from the father, when the baby’s blood comes into contact with her blood. This can happen at any time during pregnancy or birth and leads to the mother developing maternal antibodies against her baby’s platelets.
FNAIT occurs when maternal antibodies cross the placenta and attack the fetus’s blood platelets, as early as 14 weeks’ gestation. This causes the baby’s blood platelet count to drop, which means that the baby’s blood no longer clots correctly.
FNAIT prevention during pregnancy
First-line treatment of FNAIT during pregnancy is the administration of intravenous immunoglobulin (IVIG) to the mother, with or without corticosteroids. Intrauterine transfusions are considered too high-risk, as bleeding and miscarriage can occur.
Learn more about FNAIT treatment and care
The main objective is to prevent severe thrombocytopenia in the fetus and newborn, which can lead to intracranial hemorrhage (ICH). FNAIT is estimated to occur in one in 1000 to one in 1500 live births, and ICH is estimated to occur in one in 10,000 live births. ICH can cause long-term brain damage and death, in the most severe cases.
Preparing for delivery
As there is no standard testing for FNAIT, unless there is a family history or a previous affected pregnancy, the disorder can often go undetected until delivery. When FNAIT has already been diagnosed and the risk is considered high or very high, a cesarean birth is recommended. The cesarean is performed between 36 and 38 weeks’ gestation, depending on the level of risk, to prevent the baby from suffering further damage from the anti-platelet antibodies.
In cases in which the risk is lower, fetal blood sampling may be conducted at 32 weeks to determine whether a vaginal birth is possible. If the fetal blood count is considered safe enough to minimize the risk of fetal bleeding during labor and birth, a vaginal birth will be offered as an option. However, no studies have shown that a vaginal birth increases the risk for ICH.
Post-delivery
Following delivery, immediate treatment is essential to ensure the best outcomes. If ICH occurs, the consequences can be irreversible. An urgent transfusion of platelets without the specific HPA antigen will be administered for severe cases of thrombocytopenia.
