Pregnancy VTE Exclusion Pathway

Excluding VTE in pregnancy, where the usual rules do not hold · v1.2

  • Wells and PERC are not valid in pregnancy. This tool exists because of that.
  • Enter the clinical findings, and it applies the LEFt rule for suspected DVT and the pregnancy-adapted YEARS algorithm for suspected PE, to exclude thrombosis with the least foetal radiation exposure.
  • Because RCOG Green-top 37b starts treatment on suspicion rather than on a result, the tool also carries the therapeutic low molecular weight heparin dose by booking weight, the anti-Xa rule, the intervals that govern a spinal or an epidural, and the duration.
  • It stops at the first dose and the duration: it does not cover thrombolysis or the collapsed patient.

  • Risk assessment and thromboprophylaxis in a woman who has no symptoms, which is the subject of a separate RCOG guideline.
  • The management of a confirmed clot beyond the first dose and the duration.
  • Thrombolysis, and the woman who has collapsed with a massive pulmonary embolism.
  • Exclusion of DVT on the LEFt rule alone. The external validation concluded that the rule should not be used as a stand-alone test to exclude DVT in pregnancy, which is why a LEFt score of 0 on this page still goes to ultrasound.

1. Target Pathology

2. Clinical Evaluation

Evidence & Pearls

1. Pathophysiology: Why the LEFT Leg?

Over 80% of deep vein thromboses during pregnancy occur in the left lower extremity. The left common iliac vein is caught between the right common iliac artery in front of it and the expanding uterus, which is May-Thurner anatomy made worse by pregnancy. Outside pregnancy the two legs are affected about equally. That asymmetry is the reason the LEFt rule scores a left leg at all, and it is why a right-sided presentation deserves a second look rather than reassurance.

2. Practice Advisory: Why D-Dimer Stops Helping Late in Pregnancy

D-dimer rises steadily through a normal pregnancy, part of the physiological hypercoagulability that prepares for placental separation. By the late 2nd and 3rd trimesters it is often above 500 ng/mL in a woman with nothing wrong with her. So late in pregnancy a raised D-dimer rules out very little. Expect to go on to imaging anyway, and say so to her before you send the sample, rather than offering the blood test as the thing that will settle the question.

3. Illness Scripts: Dyspnoea in Pregnancy

Pulmonary Embolism
Presentation: Sudden onset dyspnoea, pleuritic chest pain, tachycardia out of proportion to baseline pregnancy elevation.
Discriminator: Hypoxaemia. (Normal pregnancy causes hyperventilation but NOT hypoxaemia).
Physiological Dyspnoea of Pregnancy
Presentation: Gradual onset "air hunger", mostly in 3rd trimester. Patient feels they cannot take a deep breath.
Discriminator: Normal O₂ saturation, normal lung exam, no sudden acute decompensation.
Peripartum Cardiomyopathy
Presentation: Dyspnoea on exertion, orthopnoea, paroxysmal nocturnal dyspnoea appearing late in pregnancy or early postpartum.
Discriminator: Basilar crackles, JVP elevation, peripheral oedema (bilateral).
Abbreviations CTPA (Computed Tomography Pulmonary Angiography) · DDU (D-Dimer Units) · DVT (Deep Vein Thrombosis) · FEU (Fibrinogen Equivalent Units) · FOGSI (Federation of Obstetric and Gynaecological Societies of India) · JVP (Jugular Venous Pressure) · LEFt (Left Leg, Oedema, First Trimester Rule) · O₂ (Oxygen) · PE (Pulmonary Embolism) · PERC (Pulmonary Embolism Rule-out Criteria) · V/Q (Ventilation/Perfusion Scan) · VTE (Venous Thromboembolism)
References
  1. van der Pol LM, Tromeur C, Bistervels IM, et al. Pregnancy-Adapted YEARS Algorithm for Diagnosis of Suspected Pulmonary Embolism. N Engl J Med. 2019;380(12):1139-1149.
  2. 2025 ESC Guidelines for the management of cardiovascular disease and pregnancy, section 11.4, management of acute venous thromboembolism. Eur Heart J. 2025.
  3. Creager MA, Barnes GD, Giri J, et al. 2026 AHA/ACC/ACCP/ACEP/CHEST/SCAI/SHM/SIR/SVM/SVN Guideline for the Evaluation and Management of Acute Pulmonary Embolism in Adults. J Am Coll Cardiol. 2026;87(13):1626-1710.
  4. Chan WS, Lee A, Spencer FA, et al. Predicting deep venous thrombosis in pregnancy: out in "LEFt" field? Ann Intern Med. 2009;151(2):85-92.
  5. Righini M, Jobic C, Boehlen F, et al. Predicting deep venous thrombosis in pregnancy: external validation of the LEFT clinical prediction rule. Haematologica. 2013;98(4):545-548.
  6. Royal College of Obstetricians and Gynaecologists. Thrombosis and Embolism during Pregnancy and the Puerperium: Acute Management. Green-top Guideline No. 37b. London: RCOG; April 2015.
  7. There is no Indian national guideline on venous thromboembolism in pregnancy. The Good Clinical Practice Recommendations of the Federation of Obstetric and Gynaecological Societies of India and the Indian College of Obstetricians and Gynaecologists were listed at fogsi.org on 2 September 2026 and carry nothing on thrombosis, thromboprophylaxis or anticoagulation in pregnancy. Indian obstetric practice follows the RCOG Green-top guidelines, which is what this pathway is built on. Until 2 September 2026 this list carried a FOGSI Good Clinical Practice Recommendation on venous thromboembolism in pregnancy and the puerperium. No such document could be found, in 2019 or in any other year, and it has been removed.
How to Cite This Tool

DOIhttps://doi.org/10.5281/zenodo.22401584

AMA Style:Umakanth S. Pregnancy VTE Exclusion Pathway. Version 1.2. MEDiscuss Clinical Decision Support System. Published 2026. Accessed . https://mediscuss.org/cdss/gravid-vte. doi:10.5281/zenodo.22401584

Vancouver Style:Umakanth S. Pregnancy VTE Exclusion Pathway [Internet]. Version 1.2. MEDiscuss.org; 2026 [cited ]. Available from: https://mediscuss.org/cdss/gravid-vte. doi:10.5281/zenodo.22401584

Disclaimer and scope
Disclaimer: This decision-support system is written for healthcare professionals. It does not substitute clinical judgment, and the treating physician retains absolute responsibility for every diagnostic, dosing and therapeutic decision. The algorithms are built on the evidence as it stands, and the evidence moves. Verify the output against your current institutional protocol, and against the patient in front of you.
© 2026 MEDiscuss.org. All rights reserved. Provided free of charge for clinical use. Unauthorised reproduction or redistribution is strictly prohibited.
Category Risk Scores & Diagnostic PathwaysPathway
Specialties Internal Medicine, Cardiology, Obstetrics & Gynaecology

Written and maintained by

Dr Shashikiran Umakanth

Last revised 24 August 2026

How these tools are written and reviewed

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