VTE Risk in Pregnancy Calculator — RCOG Thromboprophylaxis Score
Estimate VTE (deep vein thrombosis and pulmonary embolism) risk in pregnancy and postpartum using weighted risk factors from the RCOG Green-top Guideline 37a (2015). The total score guides thromboprophylaxis decisions — low (< 2), intermediate (2–3) or high (≥ 4) risk.
Previous VTE (DVT or PE) (+4)
Known high-risk thrombophilia (antiphospholipid syndrome, protein C/S deficiency, antithrombin deficiency) (+3)
Medical comorbidity (cancer, heart failure, SLE, inflammatory bowel disease, nephrotic syndrome, sickle cell, IV drug user) (+3)
IVF / ART conception (+2)
Pre-eclampsia in current pregnancy (+2)
Multiple pregnancy (+2)
Caesarean section (current delivery) (+2)
Prolonged labour (> 24 hours) (+1)
Postpartum haemorrhage (> 1 litre or transfusion) (+1)
Preterm birth in current pregnancy (+1)
Stillbirth in current pregnancy (+1)
BMI > 35 kg/m² (+2)
BMI > 40 kg/m² (+1)
Age ≥ 35 years (+1)
Parity ≥ 3 (+1)
Smoker (+1)
Varicose veins (gross) (+1)
Immobility / long-distance travel (> 4 hours) in pregnancy (+1)
Hyperemesis / dehydration (+1)
Current systemic infection (+1)
Risk level: Low
- 1
High-risk factors (3–4 pts each)
0Previous VTE = 4 pts; high-risk thrombophilia or medical comorbidity = 3 pts each. - 2
Moderate-risk factors (2 pts each)
0IVF, pre-eclampsia, multiple pregnancy, caesarean section. - 3
Low-risk factors (1 pt each)
0BMI > 35, age ≥ 35, smoking, immobility, and similar single-point factors. - 4
Total VTE risk score
0 + 0 + 0 = 0
How does this calculator work?
VTE risk score sums weighted risk factors (previous VTE, thrombophilia, obstetric factors, BMI, age, etc.) based on RCOG 2015 guidelines. Score < 2 = low (no routine prophylaxis); 2–3 = intermediate (consider LMWH in third trimester); ≥ 4 = high (LMWH from early pregnancy). Always confirmed by clinical review.
Formula
How this is calculated
Pregnancy increases VTE risk by 4–5 fold compared to non-pregnant women of the same age, and the risk rises further in the postpartum period (up to 20-fold in the 6 weeks after delivery). The Royal College of Obstetricians and Gynaecologists (RCOG) published Green-top Guideline 37a in 2015 recommending a structured risk-factor assessment to identify women who would benefit from low molecular weight heparin (LMWH) thromboprophylaxis.
The scoring system assigns weighted points to pre-existing conditions (previous VTE, thrombophilia, significant comorbidities) and obstetric or general risk factors (caesarean section, BMI > 35, age ≥ 35, multiple pregnancy, etc.). The threshold scores of 2 and 4 define three risk bands: low (no routine prophylaxis), intermediate (consider 3rd-trimester or 10-day postpartum LMWH) and high (extended antenatal and/or postnatal LMWH).
This calculator uses approximate point values that reflect the guideline's tabulated weights for educational reference. The actual clinical decision incorporates individual bleeding risk, gestational timing, patient preferences, local protocols and specialist input. This tool should never replace a consultation with an obstetrician or haematologist.
Frequently asked questions
Pregnancy causes hypercoagulability (increased clotting factors, decreased natural anticoagulants), venous stasis from the growing uterus compressing pelvic veins, and endothelial injury during delivery. All three components of Virchow's triad are active, making pregnancy one of the highest-risk VTE states in medicine.
Low molecular weight heparin (e.g. enoxaparin, dalteparin) is the preferred anticoagulant in pregnancy because it does not cross the placenta, unlike warfarin. It is the standard pharmacological thromboprophylaxis recommended by RCOG and ACOG guidelines for high-risk pregnant women.
VTE risk peaks in the first 1–3 weeks postpartum and remains elevated for at least 6 weeks after delivery. Caesarean section, postpartum haemorrhage and immobility each independently increase the risk during this window, which is why the RCOG score reassesses risk after delivery.
Also known as
TG we-Calculate Editorial Team. (2026). VTE Risk in Pregnancy Calculator — RCOG Thromboprophylaxis Score [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/vte-risk-pregnancy-calculator
TG we-Calculate Editorial Team. "VTE Risk in Pregnancy Calculator — RCOG Thromboprophylaxis Score." TG we-Calculate. 2026. https://we-calculate.com/calculator/vte-risk-pregnancy-calculator.
TG we-Calculate Editorial Team, "VTE Risk in Pregnancy Calculator — RCOG Thromboprophylaxis Score," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/vte-risk-pregnancy-calculator
@misc{wecalculate_vte_risk_pregnancy_calculator, title = {VTE Risk in Pregnancy Calculator — RCOG Thromboprophylaxis Score}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/vte-risk-pregnancy-calculator}}, year = {2026}, note = {TG we-Calculate} }
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