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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.

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
  • Dmpsey EM and Barrington K. Shortand long term outcomes follwoing 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

Centre of Clinical Excellence - Women and Children
Safer Care Victoria

Version history

First published: May 2015

Last web update: October 2018

Review by: December 2020

Uncontrolled when downloaded

Page last updated: 12 Nov 2020

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