Fetal and Neonatal Alloimmune Thrombocytopenia (NAIT)
Fetal and Neonatal Alloimmune Thrombocytopenia (NAIT) is a blood disorder affecting pregnant women and their babies. NAIT causes destruction of platelets in the fetus or newborn due to a mismatch between the mother’s platelets and the baby’s platelets. The mother’s immune system recognizes the baby’s platelets as foreign and develops antibodies that attack the baby’s platelets. NAIT is usually triggered when the mother is exposed to the baby’s blood during delivery.
Symptoms of NAIT
Fetal and Neonatal Alloimmune Thrombocytopenia (NAIT) can present as mild with the most common sign being bleeding into the skin (petechiae) or localized swelling (hematoma). More severe cases may cause the baby to bleed into the brain or major organs. These bleeding episodes can be life threatening.
Universal screening does not include Fetal and Neonatal Alloimmune Thrombocytopenia (NAIT) and as such, the first case of NAIT in a family is usually unexpected. There is a high risk for recurrence with subsequent pregnancies. Maternal and paternal platelet antigen phenotyping and screening of the maternal serum for anti-platelet antibodies can be performed. Additionally, platelet antigen genotyping can be performed on the maternal and paternal blood to determine the exact nature of the incompatibility. Neonatal platelet counts on laboratory testing are typically under 20,000 platelets/μL. Higher counts may suggest a different diagnosis, such as maternal immune thrombocytopenic purpura.
Management for subsequent at-risk pregnancies include planned delivery, avoidance of platelet reducing medications including non-steroidal anti-inflammatory drugs and aspirin. Receiving immune globulin administered into the blood stream intravenously (IVIG) during the pregnancy at a dose of 1gm/kg weekly beginning at 16 – 28 weeks of pregnancy and continuing until delivery has been shown to help reduce or alleviate the effects of Fetal and Neonatal Alloimmune Thrombocytopenia (NAIT) in infants and reduce the severity of thrombocytopenia. After birth neonates are screened for intracranial hemorrhage and have their platelet count monitored. Neonates may need platelet transfusions or treatment with IVIG.
- Espinoza JP, Caradeux J, Norwitz ER, Illanes SE. Fetal and neonatal alloimmune thrombocytopenia. Rev Obstet Gynecol. 2013;6(1):e15-e21.
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