Fetuses begin making platelets 5 days post conception and reach adult levels by 22w gestation
For this reason, the definition of thrombocytopenia has the same parameters as adults
Platelet counts increase with increasing postnatal age
Recent studies questioning the validity of using adult parameters for neonates, but no change in definition yet
Normal term neonates have incidence of thrombocytopenia <1% while the incidence for NICU admits is 18-35%
Most cases are mild and resolve within 7-14 days, but a small subset of cases (2.5-5%) are severe and take months to resolve
Severe, persistent, and symptomatic patients must be evaluated
Etiology
Increased Platelet Destruction
Alloimmune thrombocytopenia: maternal ab against fetal platelets
Neonatal Alloimmune Thrombocytopenic Purpura (NATP): fetal platelets contain an antigen inherited from the father that the mother lacks. Mother makes IgG against the paternal antigen which crosses the placenta and causes thrombocytopenia
Infants are at risk for intracranial hemorrhage. 25-50% occur in utero
Autoimmune thrombocytopenia: maternal ab against maternal and fetal platelets
SLE, ITP: maternal ab against maternal and fetal platelets
Infiltrative Disorders: neoplasms. Rare in the neonatal period.
Toxic injury to megakaryocytes by infections/drugs
Miscellaneous Causes
Neonatal Cold injury: mechanism unclear
Asphyxia: mechanism unclear, but possibly related to hypoxic injury
Von Willebrand Disease: platelet aggregation
Preeclampsia: nadir at 2-4 days with resolution typically by 7-10 days
Dilution
Management
Initial evaluation
Thorough history and physical exam of mother and neonate, including birth history
Healthy appearing infant more likely to have congenital/immunologic mediated cause
Ill appearing infant more likely to have infection, DIC, NEC, asphyxia as cause
Labs:
Neonate: CBC (repeated to confirm thrombocytopenia), platelet ag typing, peripheral smear, coags, sepsis work up if ill appearing, eval for congenital infection, genetic testing
Maternal: CBC (repeated to confirm thrombocytopenia if present), platelet ag typing
Cranial US to evaluate for IVH. If present, low threshold for transfusion. Repeat prior to discharge
Treatment
If underlying cause known (mom with SLE, ITP, known infection, etc), treat.
Platelet counts should be more aggressively maintained for first 72-96 hours of life as risk for IVH highest in this time period. If no IVH, then clinical situation used to guide need for transfusion
High dose IVIG for 3-4 days is used as adjunct
Methylprednisolone used only in emergency situations as evidence lacking
When to transfuse?
No clear guidelines
Term infant, healthy, no other risks for hemorrhage: typically if <30,000
Preterm, ill, or with other risk factors: typically if <50,000
Benefit of platelet transfusion not clearly established; some recent suggestion that transfusion may be harmful
Other therapies
IVIG, steroids, exchange transfusion typically used for immune mediated causes
Current research into using thrombopoeitic mimetics as an alternative to transfusion
References
Murphy S. Consultation with the Specialist. Thrombocytopenia. Pediatrics in Review. Feb 1999; 20(2): 64-68.
Albert TS. Throbopoietin in the Thrombocytopenic Term and Preterm Newborn. Pediatrics. June 2000; 105(6): 1286-1291.
Silver RM. Neonatal Alloimmune Thrombocytopenia: Antenatal Management. American Journal of Obstetrics and Gynecology. May 2000; 182(5): 1233-1238.
Behrman: Nelson Textbook of Pediatrics, 16th ed (2002). Philadelphia: W.B. Saunders Company.
Gomella: Neonatology: Management, Procedures, On-Call Problems, Diseases and Drugs, 4th ed (1999). McGraw-Hill/Appleton and Lange.
Ferrar-Marin F, et al. Neonatal Thrombocytopenia and Magakaryocytopoeisis. Seminar in Hematology. July 2010; 47 (3) 281-288