Neonatal Alloimmune Thrombocytopenia Diagnosis and Management

Clinical Presentation and Diagnosis

The International Society on Thrombosis and Haemostasis defines suspected neonatal alloimmune thrombocytopenia (NAIT) cases as having a nadir platelet count below 100 × 10⁹/L at birth or within 7 days, with most affected infants having counts less than 50 × 10⁹/L 1, 2, 3.
Severe isolated thrombocytopenia with normal coagulation studies excludes vitamin K deficiency bleeding and hemophilia A 1, 2.
NAIT is the most common cause of severe thrombocytopenia in term newborns, occurring in approximately 1 in 1,000 live births, although the exact incidence may vary 4, 5.

The American Academy of Pediatrics recommends administering IVIG 1 g/kg immediately for platelet counts <20,000/μL with clinical hemorrhage, with repeat dosing if necessary 4, 7, 6.
Urgent transcranial ultrasonography is recommended to assess for intracranial hemorrhage in newborns with platelet counts <50,000/μL 4, 5, 7, 6.
All intramuscular injections, including vitamin K, should be avoided until the platelet count improves 4, 5, 7.
Serial monitoring of platelet counts is necessary as they typically nadir between days 2-5 after birth 4, 5, 7, 6.

HPA genotyping from mother, neonate, and father should be performed to identify platelet antigen incompatibility 2, 3.
Maternal serum alloantibody testing using two different serological methods is recommended 7.
Crossmatch with paternal platelets can help detect alloantibodies to low-frequency antigens 7.