VTE risk score in pregnancy
Estimate the RCOG obstetric venous thromboembolism risk score for pregnancy or the postpartum period, including BMI-dependent obesity points and threshold context.
Patient details
Score breakdown
| Category | Selected factors | Points |
|---|---|---|
| Pre-existing | Age > 35 years; obesity from BMI | 2 |
| Obstetric | Pre-eclampsia in current pregnancy | 1 |
| Transient | Current systemic infection | 1 |
Selected risk factors
| Risk factor | Group | Points |
|---|---|---|
| Obesity (BMI 33.1 kg/m²) | Pre-existing | 1 |
| Age > 35 years | Pre-existing | 1 |
| Pre-eclampsia in current pregnancy | Obstetric | 1 |
| Current systemic infection | Transient | 1 |
How to use the VTE risk score in pregnancy calculator
What this calculator does
This calculator implements the obstetric VTE point assignments published by the Royal College of Obstetricians and Gynaecologists. It totals relevant pre-existing, obstetric, and transient factors, adds the obesity contribution from BMI, and shows the score threshold appropriate to pregnancy or the postpartum period. It is useful for structured documentation and for seeing exactly which factors create the total. It does not estimate an individual percentage probability, diagnose a blood clot, decide whether anticoagulation is safe, or replace clinician review. The underlying method and management context are described in RCOG Green-top Guideline No. 37a.
When to use it
Use it when documenting an early-pregnancy assessment, when a new illness or obstetric complication changes risk, around hospital admission or discharge, or when risk is reassessed immediately after birth. It can also support teaching by separating pre-existing, obstetric, and transient contributions. A single saved score should not be treated as permanent because pregnancy, delivery, admission, infection, mobility, and other factors can change.
How to calculate
- The calculator opens with a complete demonstration case and an immediately available example XLSX. Choose Patient's current situation: Pregnant (antenatal) or After birth (postnatal).
- Enter BMI directly, or enter Height in centimetres and Weight in kilograms. When both height and weight are valid, the calculator uses the full-precision BMI derived from them while displaying one decimal place. Numeric fields use a dot for decimals; commas, units, and scientific notation are rejected rather than silently reinterpreted.
- Tick every current risk factor. Delivery-outcome factors are available postnatally; ART/IVF, hyperemesis, and OHSS are available antenatally. The result updates immediately.
- Read Total VTE risk score, the threshold context, category subtotals, and detail tables. Download Excel exports the current validated model. Reset clears the demonstration data and all selected factors; after Reset, Excel export stays disabled until a complete valid BMI-based state is entered again.
Input guide
Patient's current situation is required and selects antenatal or postnatal threshold logic. Height is optional, 100 – 230 cm; Weight is optional, 30 – 300 kg. If both are present they determine BMI, so changing either can change obesity points. BMI is required when a complete height-and-weight pair is not available and accepts 10 – 80 kg/m². BMI below 30 adds 0 points, 30 – 39.9 adds 1 point, and 40 or more adds 2. A common input mistake is pasting “1,5”, “90 kg”, or scientific notation; use plain decimals such as 165, 90, and 33.1.
The Pre-existing risk factors are: Previous VTE, except a single event related to major surgery (4 points); Previous VTE provoked by major surgery (3); Known high-risk thrombophilia (3); Relevant medical comorbidity (3); Family history of unprovoked or estrogen-related VTE in a first-degree relative (1); Known low-risk thrombophilia, no VTE (1); Age > 35 years (1); Parity ≥ 3 (1); Smoker (1); and Gross varicose veins (1). The two previous-VTE choices represent alternative histories, so selecting one clears the other. Relevant comorbidity follows guideline examples such as cancer, heart failure, active SLE, inflammatory disease, nephrotic syndrome, type 1 diabetes with nephropathy, sickle cell disease, or current intravenous drug use.
The Obstetric risk factors are Pre-eclampsia in current pregnancy (1), ART/IVF (antenatal only) (1), Multiple pregnancy (1), Caesarean section in labour (2), Elective caesarean section (1), Mid-cavity or rotational operative delivery (1), Prolonged labour > 24 hours (1), PPH > 1 litre or transfusion (1), Preterm birth < 37+0 weeks in current pregnancy (1), and Stillbirth in current pregnancy (1). The caesarean choices are mutually exclusive. Delivery-outcome items are disabled during an antenatal assessment so events that have not happened do not inflate the score.
The Transient risk factors are Surgical procedure in pregnancy or puerperium, excluding immediate perineal repair (3), Hyperemesis (3), OHSS (first trimester only) (4), Current systemic infection (1), and Immobility or dehydration (1). Hyperemesis and OHSS are restricted to antenatal mode, with OHSS specifically representing the first-trimester risk item. Check transient factors only while they are clinically present or relevant to the assessment.
Output guide
Total VTE risk score is the exact sum of active point contributions. The guideline context reports only the numerical threshold: antenatally, 4 or more is linked to considering thromboprophylaxis from the first trimester and 3 to considering it from 28 weeks; postnatally, 2 or more is linked to considering thromboprophylaxis for at least 10 days. The header pills repeat Situation, BMI, Selected factors, and Score. Pre-existing points, Obstetric points, and Transient points are category subtotals. Obesity score from BMI is the automatic BMI contribution. In Score breakdown, Category identifies the group, Selected factors names its active items, and Points is the subtotal. In Selected risk factors, Risk factor identifies each active item, Group shows its category, and Points shows the individual contribution. Zero means no active scored points in that output; it does not mean zero clinical VTE risk.
Worked example
The opening demonstration is antenatal, with height 165 cm and weight 90 kg. Their full-precision BMI is about 33.06 kg/m², displayed as 33.1, so obesity contributes 1 point. Age > 35 years contributes 1, Pre-eclampsia in current pregnancy contributes 1, and Current systemic infection contributes 1. The total is therefore 1 + 1 + 1 + 1 = 4 points, so the first-open threshold message is the antenatal ≥4 message. If weight were reduced enough for BMI to fall below 30 while the three checked factors remained, the score would fall to 3 and the threshold message would change.
Learn more
For a concise version of the scoring table, see the RCOG obstetric thromboprophylaxis risk assessment tool hosted by NICE. For patient-facing background on pregnancy-related clot risk and warning signs, see the CDC guide to blood-clot risk with pregnancy.
Interpreting the result
The numerical score is not a substitute for the guideline's higher-risk pathways. Previous VTE, higher-risk thrombophilia, significant family history, hospital admission, bleeding risk, renal impairment, delivery planning, and local maternity protocols can alter management. RCOG recommends reassessment in early pregnancy, when admitted to hospital or when intercurrent problems develop, and again intrapartum or immediately postpartum. The RCOG patient information on reducing venous thrombosis risk explains prevention and low-molecular-weight heparin in patient-facing language.
Symptoms need clinical assessment
If someone may already have a DVT or pulmonary embolism, do not use this prophylaxis score to rule it in or out. Sudden shortness of breath, chest pain, coughing up blood, fainting, or a painful swollen limb require prompt assessment. The NHS pulmonary embolism guidance describes urgent warning signs and emergency actions. This calculator is educational and supports risk-factor documentation; it does not provide diagnosis, treatment, or individualized medical advice.