Neonatal Alloimmune Thrombocytopenia


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Background Presentation Differential Diagnosis Investigation
Management References Index of Related Documents

  • Low platelet count in an otherwise healthy term newborn is due to NAIT until proven otherwise.
  • Urgent matched platelet transfusion should be discussed with specialist on call at all times.



The commonest mode of presentation is probably the well neonate with bruises or petechiae.  However the spectrum of disease ranges from sub-clinical moderate thrombocytopenia to catastrophic intracranial hemorrhage (ICH) and death. A high index of suspicion is essential in all cases of active bleeding, but also in asymptomatic laboratory diagnosed thrombocytopenia. A history of thrombocytopenia in a previous sibling makes the diagnosis almost certain.

Modes of presentation
  • Previously affected sibling
  • Recurrent fetal loss
  • Antenatal ICH/hydrocephalus
  • Stillbirth
  • Bruising/bleeding neonate
  • Excessive haematoma at injection site
  • Disseminated intravascular coagulopathy
  • Postnatal ICH (silent or presenting with seizures, etc)

Differential Diagnosis

Also see Neonatal Thrombocytopenia protocol


FBC to confirm platelet count
Maternal FBC likely to have been performed during pregnancy. Maternal platelet count is normal in NAIT.
  • Definitive diagnosis of NAIT depends on parental testing.
  • In most cases the lab prefers to do this prior to platelet transfusion, but discussion with haematologist on call is necessary to arrange urgent testing.
Maternal blood samples 3 x CPD (yellow) and 1x plain (red) tubes for anti-platelet antibodies and genotyping.
Paternal blood samples 3 x CPD (yellow) tubes for genotyping.
If no paternal blood available, send 1 x CPD (yellow) tube for platelet grouping.


Platelet Count (x109) Action
<30 Transfuse
30-49 Transfuse if any bleeding
50-99 Transfuse if major bleeding
>99 Do not transfuse

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1 Williamson, L.M., et al., The natural history of fetomaternal alloimmunization to the platelet-specific antigen HPA-1a (PlA1, Zwa) as determined by antenatal screening. Blood, 1998. 92(7): p. 2280-7.
2 Murphy, M.F., S. Verjee, and M. Greaves, Inadequacies in the postnatal management of fetomaternal alloimmune thrombocytopenia (FMAIT). Br J Haematol, 1999. 105(1): p. 123-6.
3 Management of alloimmune neonatal thrombocytopenia. Lancet, 1989. 1(8630): p. 137-8.
4 Bussel, J.B., et al., Fetal alloimmune thrombocytopenia. N Engl J Med, 1997. 337(1): p. 22-6.
5 Roberts, I.A. and N.A. Murray, Thrombocytopenia in the newborn. Curr Opin Pediatr, 2003. 15(1): p. 17-23.