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Key messages

  • Polycythaemia is defined as a venous haematocrit greater than 65 per cent.
  • Polycythaemia may result in increased blood viscosity.
  • Most cases of polycythaemia occur in normal healthy infants and may result from a variety of reasons.
  • There is some controversy around the use of partial exchange transfusion to treat polycthaemia.
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    In June 2023, we commenced a project to review and update the Maternity and Neonatal eHandbook guidelines with a view to completion in 2024. Please be aware that pending this review, some of the current guidelines may be out of date. In the meantime, we recommend that you also refer to more contemporaneous evidence.

    Polycythaemia is an abnormally high level of red blood cells. It is defined as a venous haematocrit greater than 65 per cent and occurs in 0.4-4 per cent of newborn infants.

    This may result in increased blood viscosity and therefore reduced blood flow, impaired tissue oxygenation and a tendency to microthrombus formation exacerbated by hypoxia, acidosis and/or poor perfusion.

    Thrombosis may result in:

    • renal venous thrombosis
    • adrenal insufficiency
    • necrotising enterocolitis
    • cerebral infarction that may affect long-term neurological outcome.

    Causes of polycythaemia

    Most cases of polycythaemia occur in normal healthy infants and may result from a variety of reasons.

    Placental red cell transfusion

    Placental red cell transfusion may be caused by:

    • delayed cord clamping, which may increase blood volume and red cell mass by as much as 55 per cent
    • twin-to-twin transfusion syndrome.

    Placental insufficiency with increased fetal erythropoiesis secondary to intra-uterine hypoxia

    Placental insufficiency may occur in association with:


    Other causes of polycythaemia include:

    • maternal substance use such as smoking
    • maternal diabetes
    • large for gestational age infant
    • chromosomal abnormality (such as Down syndrome).

    Signs and symptoms

    Many polycythaemic infants are asymptomatic.

    When present, the signs and symptoms of polycythaemia are non-specific and include:


    Investigation for polycythaemia includes the following:

    • The diagnosis of polycythaemia is made on central or peripheral venous blood with a haematocrit over 65 per cent.
    • Because capillary blood haematocrit is not reliable, a peripheral venous haematocrit should be performed if the capillary haematocrit is above 65 per cent.
    • The haematocrit peaks at two hours of age, then falls by six hours of age and thereafter.


    Management issues to note:

    • Universal screening of haematocrit for polycythaemia is not warranted.
    • Many selectively test for polycythaemia in high-risk infants (such as IDM and placental insufficiency).


    Treatment for polycythaemia involves the following:

    • Use liberal fluid intake and/or partial exchange transfusion (PET) to reduce the venous haematocrit below 60 per cent.
    • Asymptomatic polycythaemic infants should have their fluid intake liberalised.
    • PET using normal saline as the replacement fluid is recommended in symptomatic infants with a haematocrit above 70 per cent.
    • PET is best performed through peripheral arterial and venous lines.

    Volume of exchange (ml) = blood volume* (observed - desired haematocrit) / observed haematocrit
    *Blood volume is:

    • 70-90 mL/kg for term infants
    • 85-110 mL/kg for preterm infants.

    Areas of uncertainty in clinical practice

    Areas of uncertainty include the following:

    • Treatment of polycythaemia with PET remains controversial. While it may improve symptoms, there is no evidence that it improves long-term outcome in either asymptomatic or symptomatic polycythaemic infants.
    • Partial exchange transfusion may be associated with earlier improvement of symptoms.
    • In spite of inconclusive evidence, some still advocate PET when the venous haematocrit is above 70 per cent in asymptomatic infants.
    • Risk of necrotising enterocolitis is probably increased by PET, so a decision should be based on symptoms and the potential for more serious complications.
    • Long-term outcome is more likely related to the underlying cause of polycythaemia.

    More information

    • American Academy of Pediatrics Committee on Fetus and Newborn. Routine Evaluation of blood pressure, hematocrit and glucose in newborns. Pediatrics 1993;92:474-6
    • Dempsey EM and Barrington K. Short and long term outcomes following partial exchange transfusion in the polycythemic newborn: a systematic review. Arch. Dis.Child. Fetal Neonatal Ed. 2006;91;2-6
    • Werner EJ. Neonatal polycythemia and hyperviscosity. Clinics in Perinatology 1995;22:693-710.
    • Wiswell TE, Cornish JD, Northam RS. Neonatal polycythemia: frequency of clinical manifestations and other associated findings. Pediatrics 1986;78:26-30
    • Wong W, Fok T, Lee CH et al. Randomised controlled trial: comparison of colloid or crystalloid for partial exchange transfusion for treatment of neonatal polycythemia. Arch Dis Child 1997;77:F115-8

    Get in touch

    Clinical Guidance Team
    Safer Care Victoria

    Version history

    First published: May 2015
    Review by: May 2018

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