Neonatal Alloimmune Thrombocytopenia
Description
Neonatal alloimmune thrombocytopenia (NAIT) is a condition in which maternal antibodies destroy fetal and neonatal platelets due to incompatibility of human platelet antigens (HPAs). Platelet counts in healthy term newborns are similar to those in adults, whereas preterm infants may have slightly lower platelet counts. NAIT occurs when the mother lacks a specific platelet antigen, most commonly HPA-1a, that is inherited by the fetus from the father.
Maternal IgG antibodies cross the placenta and enter the fetal circulation. These antibodies remain in the newborn for several days to several months, with an average duration of approximately three weeks, corresponding to the usual duration of neonatal thrombocytopenia.
Symptoms
Maternal alloantibodies destroy fetal platelets expressing the incompatible platelet antigen, resulting in thrombocytopenia. Although thrombocytopenia is usually transient, severe cases carry a high risk of bleeding, including intracranial hemorrhage and bleeding into other internal organs. NAIT occurs in approximately 1 in 5,000 live births. Platelet transfusions may be required in newborns with severe thrombocytopenia or active bleeding. Thrombocytopenia usually resolves by the third week of life; however, it may persist longer in breastfed infants because maternal antibodies may also be transmitted through breast milk.
Diagnosis
The diagnosis is based on platelet antigen (HPA) typing of the mother, father, and newborn, together with detection of maternal antiplatelet antibodies in the maternal and neonatal circulation.
Treatment and Prevention
Treatment may include corticosteroids, intravenous immunoglobulin (IVIG), transfusion of irradiated compatible platelets, and, in severe cases, exchange transfusion using HPA-compatible or thoroughly washed platelets.
In subsequent pregnancies, prenatal administration of intravenous immunoglobulin to the mother reduces the risk of recurrent neonatal alloimmune thrombocytopenia. Cesarean delivery is often recommended to reduce the risk of intracranial hemorrhage during birth.
During pregnancy, fetal platelet counts may be assessed, typically after approximately 20 weeks of gestation. If fetal thrombocytopenia is detected, the mother is treated with intravenous immunoglobulin, delivery is planned by cesarean section, and compatible platelet transfusion is administered to the newborn if indicated.
Source | Author Doctor Nikas Samuolis, reviewed by Prof. Virginijus Šapoka | Vilnius University | Faculty of Medicine | Head of the Department of Internal Medicine, Family Medicine, and Oncology