Paeds · fetal-neonatal-and-perinatal
Neonatal anaemia, polycythaemia and thrombocytopenia
Also known as Neonatal anaemia · Neonatal polycythaemia · Neonatal thrombocytopenia · Neonatal alloimmune thrombocytopenia · Neonatal hyperviscosity
Fellowship guide to the three major neonatal haematological disorders: anaemia (haemolytic disease, blood loss, underproduction and transfusion thresholds), polycythaemia and hyperviscosity syndrome (diagnosis and the controversy over partial exchange transfusion), and thrombocytopenia (neonatal alloimmune thrombocytopenia, maternal ITP, sepsis-related causes, platelet transfusion thresholds and intracranial haemorrhage prevention).
Checked against its sources on 5 Sept 2026
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Target exams
Red flags
- Pallor, poor perfusion, tachycardia, or tachypnoea in a neonate, prompting an immediate haemoglobin measurement
- A venous haematocrit above 65 per cent with lethargy, plethora, seizures, or cardiorespiratory distress
- Isolated severe thrombocytopenia in an otherwise well term neonate, which is neonatal alloimmune thrombocytopenia until proven otherwise
- Petechiae, purpura, or bleeding in a neonate, prompting urgent platelet count and intracranial imaging if alloimmune disease is suspected
- Severe neonatal jaundice after fava beans, infection, or oxidative drugs, raising glucose-6-phosphate dehydrogenase deficiency
- Previous sibling with neonatal alloimmune thrombocytopenia or unexplained neonatal intracranial haemorrhage
Life stages
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Clinical exam formats
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- Recognises pallor and tachycardia as signs of neonatal anaemia
- Identifies causes of neonatal polycythaemia
- Initiates appropriate workup for neonatal thrombocytopenia
- Applies evidence-based red cell transfusion thresholds for preterm infants
- Distinguishes neonatal alloimmune thrombocytopenia from maternal ITP
- Justifies the role and limitations of partial exchange transfusion for polycythaemia
- Neonatal anaemia investigation and transfusion thresholds
- Diagnosis and management of neonatal alloimmune thrombocytopenia
- Polycythaemia and the partial exchange transfusion controversy
- Bedside assessment of a pale neonate in the first 24 hours
- Interpretation of a full blood count and blood film in a neonate
- Counselling parents about a previous sibling with neonatal alloimmune thrombocytopenia
- Stage 1: Normal neonatal haematology and common abnormalities
- Stage 2: Causes and investigation of neonatal anaemia and thrombocytopenia
- Level 3: Management of severe haemolysis and alloimmune thrombocytopenia
- Haemolytic disease of the newborn and anti-D prophylaxis
- Red cell transfusion thresholds in preterm infants
- Neonatal alloimmune thrombocytopenia pathophysiology and treatment
- History-taking from parents of a neonate with unexpected pallor
- Communication of a platelet transfusion plan
- Structured examination of a plethoric neonate
- Neonatal anaemia differential diagnosis and investigation
- Transfusion thresholds using AAP guidance
- Management of neonatal alloimmune thrombocytopenia
- Neonatal haematological disorder resuscitation and stabilisation
- Appropriate use of blood products in neonates
- Shared decision-making about transfusion thresholds
- Canadian Paediatric Society approach to neonatal transfusion
- Platelet transfusion thresholds in the NICU
- Antenatal management of alloimmune thrombocytopenia
Overview & Definition
Three overlapping haematological problems dominate the first 28 days: anaemia, polycythaemia, and thrombocytopenia. Each can decompensate quickly, and all three may coexist in a sick preterm infant. Thresholds, trial names, and product choices are exam and safety-critical — and several widely taught numbers do not survive the primary sources. [8]
Neonatal anaemia is not given a single haemoglobin cut-off in the papers used here. What is established is that preterm infants are universally anaemic in the early postnatal weeks, driven by lower iron stores at birth and heavy laboratory phlebotomy, and that iron deficiency in this window harms the developing brain. Haemolysis (rhesus or ABO alloimmunisation, glucose-6-phosphate dehydrogenase deficiency), blood loss, and underproduction (anaemia of prematurity) remain the working mechanisms. [16]
Neonatal polycythaemia is defined on a venous haematocrit above 65 per cent. That textbook threshold is empirical rather than a statistical or outcome-derived cut-off. As venous haematocrit rises above 65 per cent, whole-blood viscosity rises and may compromise organ flow. [6]
Neonatal thrombocytopenia is a circulating platelet count below 150 times 10 to the 9 per litre. It is common in babies admitted to neonatal intensive care. Early-onset thrombocytopenia (first 72 hours) is usually placental insufficiency with reduced production; late-onset disease is usually sepsis or necrotising enterocolitis. Isolated severe thrombocytopenia in an otherwise well term neonate is fetal and neonatal alloimmune thrombocytopenia until proven otherwise. [7]
References18ShowHide
- [1]Kirpalani H Higher or Lower Hemoglobin Transfusion Thresholds for Preterm Infants. N Engl J Med, 2020.PMID 33382931
- [2]Gisslen T Anemia, Iron Supplementation, and the Brain. Clin Perinatol, 2023.PMID 37866852
- [3]Luzzatto L Glucose-6-Phosphate Dehydrogenase Deficiency. Hematol Oncol Clin North Am, 2016.PMID 27040960
- [4]de Haas M Anti-D prophylaxis: past, present and future. Transfus Med, 2014.PMID 25121157
- [5]Ozek E Partial exchange transfusion to prevent neurodevelopmental disability in infants with polycythemia. Cochrane Database Syst Rev, 2010.PMID 20091569
- [6]Mimouni FB Neonatal polycythaemia: critical review and a consensus statement of the Israeli Neonatology Association. Acta Paediatr, 2011.PMID 21457305
- [7]Stanworth SJ How I diagnose and treat neonatal thrombocytopenia. Blood, 2023.PMID 36787503
- [8]Roberts I Neonatal thrombocytopenia: causes and management. Arch Dis Child Fetal Neonatal Ed, 2003.PMID 12937037
- [9]Lieberman L Fetal and neonatal alloimmune thrombocytopenia: recommendations for evidence-based practice, an international approach. Br J Haematol, 2019.PMID 30828796
- [10]Curley A Randomized Trial of Platelet-Transfusion Thresholds in Neonates. N Engl J Med, 2019.PMID 30387697
- [11]Moore CM Two-year outcomes following a randomised platelet transfusion trial in preterm infants. Arch Dis Child Fetal Neonatal Ed, 2023.PMID 36810309
- [12]Pappas A Differential diagnosis and management of polycythemia. Pediatr Clin North Am, 2004.PMID 15275989
- [13]Sachs UJ Diagnosis and Management of Fetal and Neonatal Alloimmune Thrombocytopenia: An Update 2025. Transfus Med Hemother, 2025.PMID 41089465
- [14]Cappellini MD Glucose-6-phosphate dehydrogenase deficiency. Lancet, 2008.PMID 18177777
- [15]Krog GR Prediction of ABO hemolytic disease of the newborn using pre- and perinatal quantification of maternal anti-A/anti-B IgG titer. Pediatr Res, 2021.PMID 33173174
- [16]Widness JA Pathophysiology of Anemia During the Neonatal Period, Including Anemia of Prematurity. NeoReviews, 2008.PMID 20463861
- [17]Manapurath RM Enteral Iron Supplementation in Preterm or Low Birth Weight Infants: A Systematic Review and Meta-analysis. Pediatrics, 2022.PMID 35921671
- [18]Norton T Neonatal Alloimmune Thrombocytopenia: A Concise Review. Adv Neonatal Care, 2021.PMID 32657948