Pregnancy VTE Risk Score

Score venous thromboembolism risk antenatally or after birth, see when LMWH thromboprophylaxis is indicated and for how long, and get the weight-based dose. Built on the RCOG Green-top Guideline 37a position statement aligned with the NHS England Maternal Care Bundle.

Primary source: Royal College of Obstetricians and Gynaecologists. Green-top Guideline No. 37a. Reducing the Risk of Venous Thromboembolism During Pregnancy and the Puerperium: Position Statement. London: RCOG; [date not stated on document]. Full publication list and notes on the source are at the bottom of this page.

When is this assessment?

The score thresholds differ before and after birth. Delivery-related factors count only in the postnatal score.

Weight and BMI

Booking BMI sets the BMI score. Current weight sets the LMWH dose band.

Pre-existing risk factors

Previous VTE: choose one.

Other pre-existing factors

Obstetric risk factors

Current pregnancy
Mode of birth (postnatal score only)
Labour and birth events (postnatal score only)

Transient risk factors

Marked ‡ in the RCOG table: start LMWH and continue while the factor persists and for 7 days after.

Admission and bleeding

How the score works

Each factor carries the points in Appendix I of the RCOG position statement. Antenatally, a total of 4 or more means considering thromboprophylaxis from the first trimester, and a total of 3 means considering it from 28 weeks. Postnatally, a total of 2 or more means considering it for at least 10 days. Two rules override the score: a booking BMI of 50 kg/m² or more (LMWH through pregnancy and for 6 weeks after birth), and hospital admission with hyperemesis or another transient condition causing immobility (LMWH for the duration of risk and one further week). All three LMWH tables are reproduced from Table 1 of the statement. The evidence level for every recommendation here is guideline consensus.

Notes on the source document

  1. Hyperemesis scores 3, which falls below the antenatal first-trimester threshold of 4. The statement nonetheless says women admitted with hyperemesis should receive LMWH, within 72 hours per the Maternal Care Bundle. This tool applies the admission rule over the score.
  2. The ‡ marker (continue for 7 days after the factor resolves) is attached to surgery, ovarian hyperstimulation, systemic infection and immobility, but not to hyperemesis. The statement's text applies the same one-week continuation to hyperemesis, and the tool follows the text.
  3. Systemic infection and immobility/dehydration score 4 here. In the 2015 edition of GTG 37a each scored 1 (from general knowledge of the 2015 guideline; check against your copy). This change alone moves many admitted women above the antenatal threshold.
  4. BMI bands are printed as whole numbers (30–39, 40–49). The tool reads them as 30 to under 40 and 40 to under 50.
  5. Only assisted reproduction is labelled "antenatal only". The allocation of mode of birth, prolonged labour, postpartum haemorrhage, preterm birth and stillbirth to the postnatal score follows from their wording, not from an explicit statement in the document.
  6. The statement does not define "prolonged immobility" and gives no recommendation for antenatal scores below 3 or postnatal scores below 2. The tool says so rather than filling the gap.
  7. Dosing before the first midwife booking appointment is deferred to Element 1 of the NHS England Maternal Care Bundle, which is not reproduced in the statement and is not reproduced here.
  8. The RCOG table lists "Elective caesarean birth". This tool labels it pre-labour cesarean birth; the points are unchanged.
  9. Postnatal durations for groups other than those named in the statement (for example, women with previous VTE) remain those of the current GTG 37a, which the statement amends but does not replace.
Publications used in this tool
  1. Royal College of Obstetricians and Gynaecologists. Green-top Guideline No. 37a. Reducing the Risk of Venous Thromboembolism During Pregnancy and the Puerperium: Position Statement. London: RCOG; [date not stated on document].Primary sourceRisk score, thresholds, BMI ≥ 50 rule, hyperemesis and admission rule, Table 1 doses. Read directly from the uploaded document.
  2. Royal College of Obstetricians and Gynaecologists. Reducing the Risk of Venous Thromboembolism during Pregnancy and the Puerperium. Green-top Guideline No. 37a. London: RCOG; 2015.Parent guidelineRemains in force except where amended. Citation from general knowledge; RefVerify pending.
  3. NHS England. Maternal Care Bundle. Element 1: Venous thromboembolism. London: NHS England; [year not verified].Aligned standardSource of the BMI ≥ 50, hyperemesis (72 hours) and pre-booking dosing rules. Title as given in the statement; edition and year not verified.
  4. Knight M; UKOSS. Antenatal pulmonary embolism: risk factors, management and outcomes. BJOG. 2008;115(4):453-61.Cited by RCOGSupports extending the hyperemesis rule to other transient immobility. As cited in the statement; RefVerify pending.
  5. Ge YZ, Zhang C, Cai YQ, Huang HF. Application of the RCOG risk assessment model for evaluating postpartum venous thromboembolism in Chinese women: a case-control study. Med Sci Monit. 2021;27:e929904.Cited by RCOGCase-control validation of the RCOG model. As cited; RefVerify pending.
  6. Jacobsen AF, Skjeldestad FE, Sandset PM. Ante- and postnatal risk factors of venous thrombosis: a hospital-based case-control study. J Thromb Haemost. 2008;6(6):905-12.Cited by RCOGImmobility and other transient factors. As cited; RefVerify pending.
  7. Alsheef MA, Alabbad AM, Albassam RA, et al. Predictors of pregnancy-associated venous thromboembolism: a case-control study. Front Cardiovasc Med. 2022;9:920089.Cited by RCOGTransient risk factors. As cited; RefVerify pending.
  8. Fatokun TB, Swartz SE, Ebeid A, Cordes SA, Gimovsky AC, Sparks AD, et al. Venous thromboembolism risk factors in women with obesity who undergo cesarean delivery. Clin Appl Thromb Hemost. 2024;30.Cited by RCOGBMI bands. The statement gives no article number; RefVerify pending.
  9. Butwick AJ, Bentley J, Leonard SA, Carmichael SL, El-Sayed YY, Stephansson O, et al. Prepregnancy maternal body mass index and venous thromboembolism: a population-based cohort study. BJOG. 2019;126(5):581-8.Cited by RCOGBMI bands. As cited; RefVerify pending.