I. Maternal ITP

II. Neonatal Alloimmune Thrombocytopenia

  1. Results from maternal alloimmunization to fetal platelet antigens (HPA-1, HPA-2)
  2. Incidence 1:1,000-2,000 live births
  3. Can occur during a first pregnancy--unlike Rh-alloimmunization
  4. Maternal platelet count generally normal
  5. Neonatal thrombocytopenia usually profound; clinical manifestations usually evident within hours after birth (e.g. petechiae or ecchymoses over the presenting part)
  6. Intracranial hemorrhage occurs in 10-20% of cases; can occur in utero
  7. Recurrence risk is high in subsequent pregnancies if the subsequent fetus carries the pertinent antigen

(Source: ACOG Practice Bulletin #6, 9/99)