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Key messages

  • Thrombosis in neonates is underdiagnosed.
  • Management of each baby with thrombosis needs to be individualised.
  • Always include a consultation with a paediatric haematologist.
  • Decisions to ‘treat’ or ‘not to treat’ thrombosis are both active decisions.
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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 Please be aware that pending this review, some of the current guidelines may be out of date.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.

    Thrombosis in newborns is often underdiagnosed. Newborns comprise the largest group of children developing thromboembolic events, although the frequency is significantly less than for adults.

    The incidence reported in a commonly cited paper states approximately 2.4 per 1,000 admissions to NICU experience a symptomatic thromboembolic event. Another study reported 0.51 per 10,000 births. Approximately half are venous and half are arterial.

    These numbers are expected to rise due to increasing use of CVC, UVC and UAC.

    Venous thrombosis

    Central venous line (CVL) related thrombosis

    More than 80 per cent of venous thromboembolism (VTE) in newborns is secondary to CVLs. Endothelial damage, disrupted blood flow, thrombogenic catheter material and infusion of drugs and TPN are the possible mechanisms to thrombus formation.

    Acute effects

    Acute effects of CVL related thrombosis include:

    • loss of CVL patency
    • swelling and discolouration of affected limb
    • associated atrial thrombus, which may give rise to cardiac failure and appearance of a murmur
    • associated pulmonary embolus, which may give rise to respiratory insufficiency
    • catheter removal, which can precipitate embolic complications.

    Always consider the possibility of paradoxical emboli in neonates with PFO.

    Long-term effects

    Long-term effects of CVL related thrombosis include:

    • prominent collateral vessels
    • repeated loss of CVL patency requiring repeated replacement
    • post-thrombotic syndrome
    • portal hypertension and its sequelae are the specific long-term complications of UVC related thrombus.

    Diagnosis of VTE

    The accuracy of non-invasive methods for the diagnosis of VTEs in newborns is unknown.

    Ultrasound is the most commonly used method, its sensitivity is variable depending on the area studied. Sensitivity is high for neck vessels and very low for veins of the abdomen, pelvis and chest.

    Renal vein thrombosis (RVT)

    RVT is the second most common VTE in newborns and comprises 10 per cent of all VTEs. Issues to note:

    • Most RVT presents in the first week of life.
    • 25 per cent are bilateral.
    • Associated conditions include:
    • Presentation is with a palpable flank mass, haematuria, thrombocytopenia, proteinuria with or without renal impairment.

    Diagnosis of RVT

    Ultrasound is the most commonly used diagnostic test as it is non-invasive and has high sensitivity for an enlarged kidney, which is an important finding initially in RVT.

    Sinovenous thrombosis (SVT)

    SVT is underdiagnosed in newborns as the presentation can mimic many other non thrombotic conditions. Issues to note:

    • Commonly seen symptoms of SVT are seizures and lethargy.
    • Neurological deficit may be seen, although infrequently.
    • Extensive SVT can present with tense anterior fontanelle, dilated scalp veins and separation of sutures.
    • Perinatal asphyxia is commonly seen in association with SVT and risk is increased with sepsis and dehydration.

    Diagnosis of SVT

    MRI with venography (MRV) is the most sensitive and specific test for diagnosing SVT.

    Treatment of venous thrombosis

    Treatment issues and options:

    • There is a paucity of evidence to make specific and strong recommendations for anticoagulant treatment in newborns.
    • The efficacy of treatment and the risk of bleeding differ in newborns from that in children and adults.
    • The sites of the thrombus, presence or possibility of loss of organ function and associated conditions that may alter the bleeding risk usually influence the use and choice of therapy.
    • Therapeutic options include:
      • anticoagulation
      • thrombolytic therapy
      • no treatment.
    • Anticoagulation and thrombolytic therapy in newborns in general should only be used in tertiary level NICU after consultation with a paediatric haematologist.
    • Standard protocols are available.

    Arterial thrombosis

    Arterial thrombosis in neonates is almost always iatrogenic, secondary to arterial catheters. Issues to note:

    • In newborns umbilical arterial catheters and peripheral arterial catheters are commonly used for monitoring purposes.
    • The incidence of arterial TEs secondary to catheters is related to:
    • catheter length and material
    • catheter diameter
    • duration in the artery.

    Common presentations

    Common presentations of arterial thrombosis include:

    • loss of patency of the catheter
    • prolonged capillary refill time
    • diminished or absent pulses
    • decreased or immeasurable blood pressure
    • cool and pale limbs 
    • necrotising enterocolitis (umbilical arterial catheters)
    • hypertension (umbilical arterial catheters) may hint at decreased renal perfusion.

    Arterial TEs may need urgent attention, as there is potential risk of organ or limb loss.

    Long-term consequences

    Long-term consequences (depending on the site) of arterial TEs include:

    • claudication
    • asymmetric limb growth
    • hypertension
    • impaired renal function.

    Diagnosis of arterial thrombosis

    Diagnostic options for Thrombosis in neonates:

    • Contrast angiography t his is the ‘gold standard’ diagnostic test, although it may not be practical in critically ill newborns.
    • Doppler US is the most commonly used non-invasive method that has variable sensitivity.
    • MRI angiography is recommended for diagnosis of ischaemic neonatal stroke and is an option for pulmonary embolism.

    Peripheral arterial thrombosis diagnosis is often made on clinical grounds.

    Treatment of arterial thrombosis

    Treatment options for arterial thrombosis in neonates are:

    • Remove catheter.
    • Therapy with ultra-fine heparin or low molecular weight heparin is most commonly used (dose and monitoring is the same as for VTE).
    • Consider thrombolytic therapy if potential loss of limb or organ.
    • Thrombectomy may be an option if viability of limb is threatened.
    • Plastic surgery consultation is advised.


    All neonates with a history of thromboembolic events need follow up with emphasis on:

    • development of post-thrombotic syndrome
    • portal hypertension
    • investigation for congenital thrombophilic risk factors.


    Mortality is highest among newborns with aortic thrombosis and those with right atrial or superior vena cava thrombosis.

    Always consult a paediatric haematologist.

    More information

    Further reading

    • Andrew M, Monagle P, Brooker L. Thromboembolic complications during infancy and childhood.Hamilton, BC Decker Inc; 2000.
    • Monagle P, Chan AK, deVeber G, Massicotte MP. Andrew's Pediatric Thromboembolism and Stroke 3rd edition. Hamilton BC Decker Inc 2006
    • Vasc Health Risk Manag. 2008 December; 4(6): 13371348.

    Get in touch

    Clinical Guidance Team
    Safer Care Victoria

    Version history

    First published: September 2013
    Review by: September 2016

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