Pregnancy VTE Exclusion Pathway

Pregnancy-Adapted YEARS Algorithm & LEFt Rule · v1.2
How to use this tool: Wells and PERC are not valid in pregnancy. Enter the clinical findings and the tool 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.

1. Target Pathology

2. Clinical Evaluation

Academic Pearls & Pathophysiology

1. Pathophysiology: Why the LEFT Leg?

Over 80% of deep vein thromboses during pregnancy occur in the left lower extremity. This is due to the anatomical compression of the left common iliac vein by the right common iliac artery and the expanding gravid uterus (May-Thurner anatomy exacerbated by pregnancy). This starkly contrasts with the non-pregnant population where DVT is equally distributed.

2. [CLINICAL CAUTION] D-Dimer in the 3rd Trimester

Practice Pearl: D-dimer levels rise progressively throughout a normal pregnancy due to physiologic hypercoagulability (preparation for placental separation). By the late 2nd and 3rd trimesters, D-dimer is often naturally elevated > 500 ng/mL. Therefore, attempting to rule out VTE using D-dimer late in pregnancy has a very low yield, and you will frequently be forced to proceed to imaging regardless.

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).
Physiologic 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)
Algorithm References & Evidence Base
  1. 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. [Endorses clinical probability assessment with pregnancy-adapted YEARS, D-dimer at pregnancy-adapted thresholds and venous ultrasound to reduce CTPA. Therapeutic LMWH immediately on suspicion, continued at least six weeks postpartum and about three months in total. Catheter-directed treatment may be considered in severe PE.]
  3. Giri J, Bhatt DL, Barnes GD, 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. Circulation / J Am Coll Cardiol. 2026.
  4. Righini M, et al. Clinical prediction rules for the diagnosis of deep vein thrombosis in pregnancy: The LEFt rule. Ann Intern Med. 2013;159(8):527-531.
  5. FOGSI Good Clinical Practice Recommendations on Venous Thromboembolism in Pregnancy and Puerperium. Federation of Obstetric and Gynaecological Societies of India.
How to Cite This Tool

AMA Style:
Umakanth S. Pregnancy VTE Exclusion Pathway. MEDiscuss. Published 2026. Accessed .

Vancouver Style:
Umakanth S. Pregnancy VTE Exclusion Pathway [Internet]. MEDiscuss.org; 2026 [cited ]. Available from:

Disclaimer and scope
Disclaimer: This decision-support system is intended for healthcare professionals. It does not substitute clinical judgment. These algorithms are evidence-based, but medical knowledge evolves continuously. The treating physician retains absolute responsibility for all diagnostic, dosing, and therapeutic decisions. Always verify outputs against current institutional protocols and individual patient contexts.
© 2026 MEDiscuss.org. All rights reserved. This CDSS Module was designed and developed by Dr. Shashikiran Umakanth using the available evidence base. 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: 8 August 2026
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