• Platelet count <150 x 10⁹/L 
  • mild (platelet count 100–150 x 10⁹/L) and moderate (50–100 x 10⁹/L) thrombocytopenia occur frequently in preterm babies who are ill, and in those born to women with pregnancy-induced hypertension (PIH) 
  • severe thrombocytopenia (<50 x 10⁹/L) is uncommon, particularly in apparently healthy term babies and raises the possibility of neonatal allo-immune thrombocytopenia (NAIT; see below) 
  • ensure results are not spurious, if in doubt repeat venous sample

• Evaluation of early-onset (<72 hr after birth) thrombocytopenia (see Flowchart)
  • preterm babies with early-onset mild-to-moderate thrombocytopenia in whom there is good evidence of placental insufficiency: further investigations not warranted unless platelet count does not recover within 10–14 days
  • preterm babies without placental insufficiency: investigate first for sepsis
  • term babies: investigate for sepsis and NAIT 
• If severe thrombocytopenia, perform clotting screen
• Look for presence of active bleeding or visible petechiae
• If features suggestive of congenital infection (e.g. abnormal LFT, rashes, maternal history etc.) or if persistent or unexplained thrombocytopenia, perform congenital infection i.e. CMV and toxoplasma serology; check maternal status for syphilis, rubella and HIV; herpes simplex and enteroviral screen
• Obstetric history, particularly maternal platelet count, drugs, pre-eclampsia. Family history of bleeding disorders
• Careful examination, include other associated features (e.g. trisomies and inherited syndromes)

Evaluation of late onset thrombocytopenia

• Thrombocytopenia presenting in baby after first 3 days of life, presume underlying sepsis or NEC until proved otherwise 
  • these babies are at significant risk of haemorrhage, though the benefit of platelet transfusion is not clear-cut

Summary of investigations (also refer to text above)

General

Avoid

• Heel prick and IM injections, use venepuncture and IV injections
• Invasive procedure (central line, LP, chest drain etc.). If any of above are unavoidable:
  • discuss with on-call consultant 
  • give platelet transfusion if platelet count <50 x 10⁹/L before the procedure (if semi-elective e.g. LP, central lines) or during/soon after procedure (if emergency e.g. chest drain)
  • give particular attention to haemostasis

Platelet transfusion

• Only available for immediate and specific therapy for thrombocytopenia but carries risk of transfusion-related infections and transfusion reactions, and only after discussion with consultant

Indications for platelet transfusion (term and preterm babies)

• Main objective is to prevent consequences of severe thrombocytopenia, significant risk of acute intracerebral haemorrhage and neuromorbidity

Platelet count <25 x 10⁹/L

• In otherwise well baby, including NAIT, if no evidence of bleeding and no family history of intracranial haemorrhage

Platelet count <50 x 10⁹/L

• In baby with:
  • clinical instability 
  • concurrent coagulopathy 
  • birth weight <1000 g and aged <1 week 
  • previous major bleeding e.g. intraventricular haemorrhage (IVH) 
  • current minor bleeding (e.g. petechiae, venepuncture oozing) 
  • planned surgery, exchange transfusion or invasive procedure (central line insertion, LP, chest drain, ECMO etc.)
  • platelet count falling and likely to fall below 30 
  • NAIT if previously affected sibling with intracranial bleed
  • PDA treated with indomethacin or ibuprofen

Platelet count <100 x 10⁹/L

• If major bleeding or major surgery (e.g. neurosurgery), give platelet transfusion 

Type of platelets

• NAIT: HPA compatible platelets wherever possible
• All others: blood group-compatible CMV negative
• Irradiation of platelets is not routinely required but consider for babies with definite or suspected immunodeficiency, or those who have undergone intrauterine transfusions

Volume of platelets

• 10–20 mL/kg (10 mL/kg usually raise platelet count by >50 x 10⁹/L). Babies with suspected NAIT will require higher dose of 20 mL/kg

• Use platelets as soon as they arrive on ward (ensure IV access before requesting platelets from blood bank)
• Keep platelets at room temperature
• To minimise loss, draw contents of pack into 50 mL syringe through a special platelet or fresh blood transfusion set with a 170–200 micrometre filter and infuse, using a narrow bore extension set linked to IV line, primed with sodium chloride 0.9%
• Transfuse platelets over 30–60 min, mixing syringe from time to time to avoid platelets settling down
• There is no need for routine use of diuretic after platelet transfusion 
• Check platelet count within 12 hr after transfusion 

• Analogous to rhesus haemolytic disease and caused by transplacental passage of maternal alloantibodies directed against fetal platelet antigens, inherited from father but absent in mother
• Majority caused by antibodies against platelet antigens, HPA-1a (80%) and HPA-5b (10–15%)
• NAIT can affect first pregnancy and has 10% risk of severe intracranial haemorrhage; 20% of survivors exhibit significant neurodevelopmental sequelae

Recognition

• For HPA-1a antigen-negative women, complete a neonatal alert form
• Petechiae, purpura, excessive bleeding and severe thrombocytopenia in an otherwise healthy term newborn baby indicate NAIT until proved otherwise
• NAIT can also present with:
  • fetal intracranial haemorrhage or unexplained hydrocephalus
  • postnatal intracranial haemorrhage in term baby

Assessment

• Check baby’s platelet count daily until >100 x 10⁹/L
• Check mother’s platelet count (may already be in maternal healthcare record)
• Obtain blood from mother, baby and father for platelet typing and antibodies. Liaise with haematology department about appropriate samples
• Arrange cranial ultrasound scan (see Cranial ultrasound scans guideline)

Treatment

• In 30% of cases, maternal antibody may not be found and can be detected later 
• Transfuse baby with suspected NAIT with accredited HPA-1a antigen-negative platelets if:
  • bleeding or
  • platelet count <25 x 10⁹/L
• National Blood Service has a pool of suitable donors, and platelets are available at short notice from blood bank 
  • if accredited HPA-1a negative platelets not available, administer random donor platelets

• If thrombocytopenia severe (<50 x 10⁹/L), or haemorrhage persists despite transfusion of antigen-negative platelets, administer intravenous human immunoglobulin (IVIG) 1 g/kg/day once daily (give 1 full 2.5 g vial maximum for babies ≥2.5 kg) for 1–3 days (may require additional doses 2–4 weeks later)
• Aim to keep platelet count >25 x 10⁹/L for first week of life, or as long as active bleeding continues
• Report newly diagnosed babies with NAIT to fetal medicine consultant for counselling for future pregnancies

Clinical features

• Caused by transplacental passage of autoantibodies in women with ITP or SLE, and affecting about 10% of babies born to such women
• Severity generally related to severity of maternal disease
• Risk of intracranial haemorrhage in baby <1%

Management

• Report all women with thrombocytopenia and those splenectomised through Neonatal Alert System, and instigate plan of management 
• Send cord blood for platelet count
• Check baby’s platelet count 24 hr later, irrespective of cord blood result
• If baby thrombocytopenic, check platelet count daily for first 3–4 days or until >100 x 10⁹/L
• If platelet count <25 x 10⁹/L, whether bleeding or not, treat with IVIG (dose as in NAIT) +/-steroids
• Discharge baby when platelet count >100 x 10⁹/L
• For babies requiring IVIG, recheck platelet count 2 weeks later. A few may require another course of IVIG at this time because of persistence of maternal antibodies