About the VTE Risk Score Calculator in Pregnancy
Pregnancy and the postpartum period raise the risk of venous thromboembolism (VTE) — deep vein thrombosis and pulmonary embolism — several-fold compared with the non-pregnant state. To decide who benefits from preventive low-molecular-weight heparin (LMWH), UK maternity units commonly use a structured risk assessment modeled on the Royal College of Obstetricians and Gynaecologists (RCOG) Green-top Guideline 37a. This calculator reproduces the structure of that assessment: most risk factors contribute 1 point each (obesity with BMI 40 or higher contributes 2), while previous VTE, high-risk thrombophilia, and certain severe medical comorbidities are treated as automatic indications for antenatal prophylaxis regardless of the point total.
How the score is built
- Age points: 1 point if maternal age is 35 years or older at the time of delivery.
- BMI points: 1 point for a pre-pregnancy BMI of 30–39.9 kg/m², 2 points for a BMI of 40 kg/m² or higher.
- Parity points: 1 point for parity of 3 or more (three or more previous births at 24 weeks' gestation or beyond).
- Other risk factors: 1 point each for factors such as smoking, gross varicose veins, multiple pregnancy, current pre-eclampsia, assisted reproduction (IVF), a first-degree relative with unprovoked or estrogen-related VTE, low-risk thrombophilia, current systemic infection, immobility, long-distance travel, or a surgical procedure during pregnancy — entered here as a single count.
- Automatic high-risk triggers: a personal history of VTE, a high-risk thrombophilia, or a major medical comorbidity (such as active cancer, heart failure, active systemic lupus erythematosus or inflammatory bowel disease, nephrotic syndrome, type 1 diabetes with nephropathy, sickle cell disease, or current intravenous drug use) indicates a need for antenatal thromboprophylaxis on its own, independent of the point total.
Interpreting the result
When no automatic trigger applies, the point total maps to three bands used in RCOG-style guidance: 4 or more points suggests thromboprophylaxis from early pregnancy (first trimester) through 6 weeks postnatal; exactly 3 points suggests starting at 28 weeks' gestation; fewer than 3 points means no routine antenatal LMWH, with a focus instead on mobilization and avoiding dehydration. Any automatic trigger overrides the count and points toward starting prophylaxis from early pregnancy.
When to consult a professional
This tool performs the standard risk-factor arithmetic for education and discussion purposes only — it does not prescribe medication or replace an individualized assessment. VTE risk should be reassessed at every antenatal visit, on any hospital admission, and again after birth, since postnatal thresholds are separate and generally lower than antenatal ones. Confirm any thromboprophylaxis decision with an obstetric or haematology team using your hospital's protocol.