LEFt Rule for DVT in Pregnancy
Three-variable rule for DVT in pregnancy (Chan 2009): symptoms in the Left leg, ≥2 cm calf circumference difference (Edema), and First-trimester presentation. Score 0 has very low DVT prevalence; score ≥1 mandates duplex US.
Score interpretation
None of the 3 LEFt variables. External validation: DVT in 1 of 30 women (3%) with LEFt 0 (Le Moigne 2014).
→ LEFt is not validated to exclude DVT without imaging: compression duplex ultrasound for any suspected DVT in pregnancy (RCOG Green-top 37b).
One or more LEFt variables. External validation: DVT in 8 of 59 women (14%) with LEFt ≥ 1 (Le Moigne 2014).
→ Compression duplex ultrasound of leg veins. If negative but high clinical suspicion, repeat in 3 and 7 days. If positive, therapeutic LMWH — Adults: enoxaparin 1 mg/kg BD or dalteparin. Children: use a children's formulary. Review for duration; avoid DOACs and warfarin in pregnancy.
Interpretation bands for the LEFt. Apply clinical judgement and local guidance.
References
Related
Curated clinical cross-links plus same-class fallbacks.
- Methotrexate (Ectopic) · Antimetabolite (Ectopic Pregnancy Management)
- Hydralazine (IV — Acute Hypertension in Pregnancy) · Vasodilator (Antihypertensive)
- Methyldopa (Chronic Hypertension in Pregnancy) · Centrally Acting Antihypertensive
- Enoxaparin (VTE in Pregnancy) · Low Molecular Weight Heparin (LMWH) — VTE Prophylaxis/Treatment
- Folic Acid (Pre-conception and Pregnancy) · Vitamin / Neural Tube Defect Prevention
- Ferric Carboxymaltose (IV Iron — Pregnancy) · IV Iron Preparation — Iron Deficiency Anaemia in Pregnancy
- Acute Asthma in Adults · BTS/SIGN British Guideline on Asthma 2019; NICE NG80
- Pulmonary Embolism Assessment · NICE NG158; ESC 2019 PE Guidelines
- Acute Exacerbation of COPD (AECOPD) · NICE NG115; GOLD 2024
- Spontaneous Pneumothorax (Adult) · BTS Pleural Disease 2023
- Atypical Pneumonia (Legionella / Mycoplasma / Chlamydophila) · BTS 2023; IDSA
- COPD Exacerbation Management · NICE NG115 / GOLD 2024
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.