VTE risk in pregnancy calculator

Venous thromboembolism in pregnancy is a leading preventable cause of maternal morbidity, and antenatal services commonly estimate that risk by adding published points for body-mass index, age, previous clots, thrombophilia, and obstetric history. This pregnancy VTE risk calculator implements that additive antenatal rule as a pure function: you send a finite BMI, a finite age, and yes-or-no history flags, and you receive the integer score, a low, intermediate, or high band, and the matching low-molecular-weight heparin recommendation used in teaching—routine antenatal care, consider prophylaxis from twenty-eight weeks, or consider prophylaxis throughout pregnancy. An invalid BMI is rejected with invalid input rather than being clamped into a neighbouring obesity band.

How the antenatal VTE score is defined

The additive antenatal score implemented here follows the teaching form of the Royal College of Obstetricians and Gynaecologists Green-top Guideline on reducing venous thromboembolism during pregnancy and the puerperium. Each listed factor contributes a fixed integer; nothing is weighted by a regression coefficient and nothing is estimated from a black-box model. Previous venous thromboembolism, other than a single event provoked only by major surgery, contributes four points and by itself already reaches the high band.

Known high-risk thrombophilia—antithrombin deficiency, protein C or S deficiency, or homozygous or compound heterozygous factor V Leiden or prothrombin G20210A—contributes three points, as does a significant medical comorbidity such as cancer, heart failure, active lupus, inflammatory bowel disease, nephrotic syndrome, type 1 diabetes with nephropathy, sickle cell disease, or current intravenous drug use. Body-mass index of forty or greater contributes two points; a BMI of thirty or greater but below forty contributes one point; those two obesity bands are alternatives, never added together.

Age strictly greater than thirty-five years contributes one point. Family history of unprovoked or estrogen-related VTE in a first-degree relative, known low-risk thrombophilia, parity of three or more, current smoking, gross varicose veins, current pre-eclampsia, multiple pregnancy, and IVF or other assisted reproduction each contribute one point. Low-risk thrombophilia is not stacked on top of a high-risk lesion: if both flags are true, only the three high-risk points are counted.

The integer total then maps to a teaching anticoagulation band: four or more suggests considering prophylactic low-molecular-weight heparin throughout pregnancy and for six weeks after birth; exactly three suggests considering prophylaxis from twenty-eight weeks and for six weeks after birth; two or fewer is routine antenatal care from this score alone, with reassessment if the person is admitted or after birth.

This is educational arithmetic from the published point table, not a diagnosis, not a prescription, and not a substitute for a clinician, local protocol, or a full postnatal reassessment that adds caesarean birth, postpartum haemorrhage, or prolonged labour.

Where pregnancy VTE calculators show up in real work

Midwifery and obstetric teaching constantly assign antenatal thromboprophylaxis drills from textbook BMI, age, and history combinations, so a single trusted oracle that returns the integer beside each component speeds grading and demo setup. Simulation centres and electronic worksheet products want a documented BMI, age, and history path that clients can audit by hand rather than a black-box clot-risk model that mixes D-dimer, Wells, or revised Geneva items without disclosure.

Research assistants preparing synthetic maternity datasets need stable VTE labels from known risk factors without network calls or model drift, and they need a hard reject when BMI arrives negative or out of range so dirty extracts cannot masquerade as scores. If you later need a postnatal-only score that adds caesarean birth, postpartum haemorrhage, or stillbirth, a pulmonary-embolism pretest such as the revised Geneva score, or a pregnancy weight-gain range from BMI and weeks, treat those as separate search intents and landings rather than overloading this pregnancy VTE calculator page.

Always present results as educational estimates from the published antenatal point table; clinical decisions require qualified professionals, a full history this tool does not collect, and local thromboprophylaxis protocols that may start heparin on admission even when the outpatient score is low. Keep requests small, pin the integer score and the recommendation key in tests, and you get reproducible VTE figures for homework, LMS plugins, and edge workers without standing up a clinical information system of your own.