VTE Risk Score Calculator in Pregnancy – Thrombosis Risk Assessment
The VTE Risk Score Calculator in Pregnancy assesses venous thromboembolism (VTE) risk for pregnant women using validated clinical criteria. Enter age, BMI, parity, relevant medical history, and obstetric risk factors. Get the VTE risk score, risk category, prophylaxis recommendation, and clinical action guidance. Based on the Royal College of Obstetricians and Gynaecologists (RCOG) VTE risk assessment framework. For use by qualified healthcare professionals. All prophylaxis decisions must be made by a qualified obstetrician.
Formula
This calculator applies date/time interval logic based on your inputs.
Quick Tip
Use this output as guidance and confirm clinical decisions with a qualified professional.
Assessing VTE risk in a pregnant patient? Enter the clinical risk factors. Get the RCOG-based risk score, risk category, and prophylaxis recommendation — instantly at the point of care.
Featured Answer
Q: How do I assess VTE risk in pregnancy?
A: VTE risk in pregnancy is assessed by adding points for individual risk factors across three categories: pre-existing factors (such as prior VTE, thrombophilia, or BMI over 30), obstetric factors (such as multiple pregnancy, pre-eclampsia, or caesarean section), and transient factors (such as immobility or dehydration). Total score guides prophylaxis recommendation. Use this calculator to tally the score and get the risk category and RCOG-based guidance.
How to Use VTE Risk Score Calculator in Pregnancy
- Enter age — score 1 point for age 35 or older.
- Enter BMI — score 1 point for BMI over 30, 2 points for BMI over 40.
- Enter parity — score 1 point for three or more previous pregnancies.
- Enter medical history factors — including prior VTE, thrombophilia, or family history of VTE.
- Enter obstetric factors — including multiple pregnancy, IVF conception, pre-eclampsia, and planned or emergency caesarean.
What is VTE Risk in Pregnancy?
Venous thromboembolism (VTE) in pregnancy includes deep vein thrombosis (DVT) and pulmonary embolism (PE). Pregnancy increases VTE risk 4–5 times above baseline. The risk remains elevated for 6 weeks postpartum.
VTE is one of the leading causes of maternal death in developed countries. Many of these deaths are preventable with appropriate thromboprophylaxis.
The RCOG risk stratification framework assigns points for pre-existing, obstetric, and transient risk factors. Total score determines the recommended prophylaxis approach:
- Score < 2: mobilisation and hydration only.
- Score 2–3: consider low-molecular-weight heparin (LMWH) from 28 weeks.
- Score ≥ 4: offer LMWH throughout pregnancy from the first trimester.
Example: Age 38, BMI 34, primiparous, IVF conception, no prior VTE, no thrombophilia.
| Risk Factor | Points |
|---|---|
| Age ≥ 35 | 1 |
| BMI > 30 | 1 |
| IVF conception | 1 |
| Total Score | 3 — Intermediate Risk |
| Recommendation | Consider LMWH from 28 weeks |
VTE in Pregnancy: Risk Assessment, Prophylaxis, and Clinical Action
Why VTE Risk Score Calculator Matters
Pulmonary embolism is the leading direct cause of maternal mortality in the UK and many high-income countries. Most cases are preventable.
Systematic VTE risk assessment at every antenatal contact allows clinicians to identify women who need prophylaxis early. But calculating the score manually across multiple risk categories is error-prone under clinical time pressure.
This calculator tallies all RCOG risk categories automatically. It produces the score, risk category, and prophylaxis recommendation — all in under a minute.
How VTE Risk Score Is Calculated — Step by Step
- Sum pre-existing risk factors:
- Prior VTE: +4; thrombophilia with prior VTE: +4; high-risk thrombophilia: +3
- Age ≥ 35: +1; BMI > 30: +1; BMI > 40: +2
- Family history of VTE (first-degree): +1; parity ≥ 3: +1
- Sum obstetric risk factors:
- Multiple pregnancy: +1; IVF/ART: +1; pre-eclampsia: +1
- Caesarean section (elective): +1; emergency CS: +2
- Sum transient risk factors:
- Prolonged immobility: +1; dehydration/infection/ovarian hyperstimulation: +1
- Total score determines risk category and prophylaxis recommendation.
RCOG VTE Risk Category Reference
| Total Score | Risk Category | Recommended Action |
|---|---|---|
| < 2 | Low | Mobilisation and hydration |
| 2–3 | Intermediate | Consider LMWH from 28 weeks |
| ≥ 4 | High | Offer LMWH from first trimester |
| Prior VTE / High thrombophilia | Very High | LMWH throughout pregnancy and 6 weeks postpartum |
Common Mistakes to Avoid
- Assessing only at booking. VTE risk changes during pregnancy. Reassess at each antenatal visit and after any significant change — hospitalisation, reduced mobility, or new obstetric risk factors.
- Not reassessing postpartum. The highest-risk window is the first 6 weeks after delivery. Postpartum VTE risk must be assessed separately and prophylaxis continued as appropriate.
- Underweighting emergency caesarean. Emergency caesarean scores 2 points — double the elective rate — because of greater immobility and trauma.
- Forgetting transient risk factors. Current infection, immobility from hyperemesis, or dehydration are time-limited but clinically significant VTE risk contributors.
- Not involving haematology for complex thrombophilia. For patients with high-risk thrombophilia or prior pregnancy-associated VTE, haematology input is essential alongside obstetrician management.
When to Use This Calculator
Use this tool at the booking appointment, at each antenatal visit, and at any point where a significant new risk factor emerges. Also use it at labour admission and in the postnatal period.
VTE risk in pregnancy spans a continuum. Early identification and appropriate LMWH prophylaxis reduces maternal mortality from pulmonary embolism significantly.
For other pregnancy health assessments, the BMI in Pregnancy Calculator provides weight gain guidance. For sodium correction in obstetric critical care, the Sodium Correction Rate Calculator is the relevant clinical tool.
Pro Tips
VTE risk score — document this at every antenatal visit. It forms part of the medico-legal record and supports standardised prophylaxis decision-making.
Risk category — use the category label in handover and referral documentation. Low, intermediate, and high risk communicate urgency clearly across clinical teams.
Prophylaxis recommendation — cross-reference with your local obstetric VTE guideline. RCOG guidance is widely adopted but local protocols may have minor variations.
Clinical action — LMWH dosing for VTE prophylaxis in pregnancy uses weight-based dosing. The score triggers the decision to prescribe — the dose is then set by body weight.
Important Assumptions and Limitations
This calculator applies the RCOG Green-top Guideline No. 37a (2015) risk factor framework. It is designed for use by qualified healthcare professionals in the antenatal setting. Risk scores are additive guidance tools — they do not replace clinical judgement or full patient history. This tool is for clinical reference only. All prophylaxis decisions must be made by a qualified obstetrician. Calculation reviewed against RCOG VTE risk assessment guideline references.
For patient management decisions, consult a qualified obstetrician.
Frequently Asked Questions
Find answers to common questions about VTE Risk Score Calculator in Pregnancy
Venous thromboembolism (VTE) in pregnancy includes deep vein thrombosis and pulmonary embolism. Pregnancy increases VTE risk 4–5 times above baseline. The risk peaks in the third trimester and the 6 weeks postpartum. VTE is a leading cause of maternal mortality. Systematic risk assessment and appropriate thromboprophylaxis with low-molecular-weight heparin significantly reduces mortality.
Add points for pre-existing, obstetric, and transient risk factors using the RCOG framework. Key high-scoring factors include prior VTE (+4), thrombophilia with prior VTE (+4), age ≥ 35 (+1), BMI > 30 (+1), multiple pregnancy (+1), and emergency caesarean (+2). Total score of ≥ 4 warrants LMWH from the first trimester. This calculator tallies all categories automatically.
The calculator applies the RCOG Green-top Guideline No. 37a risk factor scoring framework. Risk score outputs are accurate when all clinical factors are correctly entered. The tool is a decision support aid — it does not replace comprehensive clinical assessment. Individual patient factors, contraindications to LMWH, and local guideline variations require clinician judgement alongside the score.
Risk category classifies the total VTE risk score into low, intermediate, or high risk. Each category has a corresponding prophylaxis recommendation. Low risk warrants mobilisation and hydration only. Intermediate risk (score 2–3) warrants consideration of LMWH from 28 weeks. High risk (score ≥ 4) warrants LMWH from the first trimester. Category is the primary communication tool across clinical teams.
VTE risk should be assessed at the booking appointment, at each antenatal visit, on admission to hospital, and postpartum before discharge. It should also be reassessed after any significant change — new obstetric complication, hospitalisation, reduced mobility, or infection. Postpartum VTE risk is highest in the first 6 weeks and must be assessed and managed separately from antenatal risk.
A score of 3 is intermediate risk. RCOG guidance recommends considering LMWH from 28 weeks of pregnancy for intermediate-risk women. The decision to start LMWH earlier — or at all — depends on the specific combination of risk factors, patient preference, and clinician judgement. Women with a score of 3 due to a single high-weight factor may be treated differently than those with three lower-weight factors.
No. Thrombophilias are weighted by risk level. High-risk thrombophilias — such as antiphospholipid syndrome with positive tests, antithrombin deficiency, homozygous Factor V Leiden, and compound heterozygous thrombophilias — score higher than low-risk thrombophilias. Prior VTE plus thrombophilia scores 4 points — the highest single category — and typically mandates LMWH throughout pregnancy.
Yes. Emergency caesarean section scores 2 points in the RCOG framework. Elective caesarean scores 1 point. Emergency CS carries higher VTE risk because of greater surgical trauma, longer operative time, and periods of immobility associated with urgent procedures. All caesarean sections are a VTE risk factor — but the emergency category warrants more aggressive prophylaxis consideration.