VTE Risk Score Calculator in Pregnancy

VTE (venous thromboembolism) includes deep vein thrombosis (DVT) and pulmonary embolism (PE). Pregnancy increases VTE risk approximately 4 to 5-fold compared to the non-pregnant state due to three physiological changes: a hypercoagulable blood state (elevated clotting factors, reduced natural anticoagulants), venous stasis from uterine compression of the inferior vena cava, and vascular wall changes. VTE is a leading cause of direct maternal death in high-income countries. The risk is highest in the first few weeks after delivery.

The RCOG score adds point values for established risk factors based on evidence from epidemiological studies. A score of 4 or above during the antenatal period is classified as high risk and indicates that LMWH thromboprophylaxis should be considered from the first trimester. A score of 2 to 3 is moderate risk and generally triggers prophylaxis from 28 weeks. A score of 0 to 1 is lower risk, requiring only mobilization and hydration without pharmacological prophylaxis.

Thromboprophylaxis means preventive treatment to stop blood clots from forming. In pregnancy, the standard method is a daily injection of low-molecular-weight heparin (LMWH), such as enoxaparin or dalteparin, given subcutaneously. Compression stockings are used as an adjunct. LMWH does not cross the placenta and is safe for the fetus. Treatment is typically started in the first trimester for high-risk women, at 28 weeks for moderate-risk women, and for 6 weeks or 10 days after delivery depending on postnatal score.

High-risk thrombophilias (3 points) include antiphospholipid syndrome (APS), homozygous Factor V Leiden mutation, combined thrombophilias, and protein C or protein S deficiency. Low-risk thrombophilias (1 point) include heterozygous Factor V Leiden, heterozygous prothrombin gene mutation, and antithrombin deficiency if controlled. Always confirm thrombophilia risk with a hematologist, as clinical context (prior VTE, family history) modifies management independently of the raw score.

A score of 0 to 1 indicates a lower background risk and does not require pharmacological thromboprophylaxis in most guidelines. However, lower-risk women should still maintain adequate hydration, avoid prolonged immobility, and promptly report symptoms of DVT (calf swelling, redness, warmth) or PE (breathlessness, pleuritic chest pain, haemoptysis) to their care team. If a new risk factor develops (hospital admission, infection, immobility), the score should be recalculated.

Previous VTE adds 4 points. Serious comorbidities (active cancer, SLE, IBD, inflammatory polyarthropathy, cardiac or pulmonary disease) add 3 points each. Hyperemesis gravidarum adds 3 points. High-risk thrombophilia adds 3 points. These four factors alone can reach the high-risk threshold of 4. Minor 1-point factors (age over 35, BMI 30 to 39, parity 3 or more, smoking, varicose veins, multiple pregnancy, IVF, pre-eclampsia, immobility, infection) accumulate to cross the threshold when combined.

Yes. Emergency cesarean section adds 2 points to the postnatal VTE score, while elective cesarean adds 1 point, per the RCOG model. A vaginal delivery adds 0 points. This reflects the additional surgical trauma and recovery period of cesarean delivery, which independently elevates thrombotic risk. A woman who otherwise has a score of 0 to 1 will move to the moderate-risk category after an emergency cesarean and should receive 10 days of postnatal thromboprophylaxis.

The duration depends on the postnatal risk score. A score of 2 to 3 warrants 10 days of LMWH. A score of 4 or above warrants at least 6 weeks. Women with a history of VTE, high-risk thrombophilia, or multiple antenatal risk factors that persist postnatally may need extended prophylaxis beyond 6 weeks, evaluated individually. Postpartum hemorrhage may complicate anticoagulation timing and should be discussed with the clinical team before restarting LMWH.

DVT symptoms include unilateral leg swelling (more common in the left leg due to anatomical pressure from the left iliac vein), pain, warmth, and redness, usually in the calf. PE symptoms include sudden breathlessness, sharp chest pain that worsens with breathing (pleuritic pain), coughing up blood, rapid heart rate, and collapse in severe cases. These symptoms overlap with normal pregnancy changes and should be urgently evaluated with compression ultrasound (for DVT) or CTPA or V/Q scan (for PE). Do not wait.

Yes. LMWH does not pass into breast milk in clinically significant amounts and is safe for breastfeeding. Women who need postnatal thromboprophylaxis while breastfeeding can continue their LMWH injection without any additional risk to the baby. Warfarin is also generally considered safe during breastfeeding, though LMWH is preferred for most postnatal VTE prophylaxis.

Yes. The RCOG score adds 1 point for BMI 30 to 39.9 and 2 points for BMI 40 or above. Higher BMI increases VTE risk through multiple mechanisms: greater venous stasis, impaired fibrinolysis, and reduced mobility. Women with a BMI above 40 are frequently considered for antenatal thromboprophylaxis from early pregnancy regardless of other risk factors. LMWH dosing is also weight-adjusted, with higher doses required for adequate anti-Xa levels in women above 100 kg.

They serve different purposes. The Wells DVT score (and modified Wells PE score) are diagnostic tools used when a patient has symptoms to estimate the pre-test probability of confirmed DVT or PE, guiding further investigations like ultrasound or D-dimer. This RCOG VTE risk score is a prophylactic screening tool used for all pregnant women to identify who needs preventive treatment before any clot develops. They are not interchangeable; if you have symptoms, contact your healthcare provider for a diagnostic evaluation.