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VTE Risk Score Calculator in Pregnancy

Created by Dominika Śmiałek, MD, PhD candidate
Reviewed by Dominik Czernia, PhD and Jack Bowater
Based on research by
Royal College of Obstetricians & Gynaecologists Reducing the Risk of Venous Thromboembolism during Pregnancy and the Puerperium - Guidelines;; April 2015
Last updated: Jan 18, 2024

Are you searching for a tool to assess venous thromboembolism (medical abbreviation VTE) risk in a pregnant patient? 🤰 This VTE risk score calculator in pregnancy is based on the Royal College of Obstetricians and Gynaecologists (RCOG) recommendations, and estimates the risk of VTE, both postpartum and during pregnancy.

Stay with us to get more information on:

  • What is venous thromboembolism?
  • What is VTE risk assessment in pregnancy?
  • What are the VTE in pregnancy guidelines?
  • How to use this VTE risk score pregnancy calculator in practice?

VTE - general information

What does VTE stand for? Venous thromboembolism, also known as VTE (medical abbreviation), is a condition caused by a pathological process called the triad of Virchow.

Virchow's triad includes:

  • Hemodynamic changes (e.g., stasis);
  • Endothelial injury/dysfunction; and
  • Changes in the constitution of blood.

The very first sign of early VTE is an episode of venous thrombosis (a blood clot in one of the veins) which comes in different forms:

  1. CVST- cerebral venous sinus thrombosis - This is a rare type of stroke, yet is often diagnosed in pregnant/postpartum women.

  2. DVT - deep vein thrombosis - The most common form of venous thrombosis, the person experiences swollen, warm, painful limbs on one side of their body.

  3. Budd-Chiari syndrome - Thrombosis of the hepatic vein sometimes leads to liver insufficiency.

What happens if the clot breaks free of the vein wall? It then becomes an embolus, and if it travels around the cardiovascular system into veins and arteries with a smaller diameter, it may block them. There are two possible consequences:

  1. Pulmonary embolism - Blockage of one of the lung arteries. The symptoms vary from shortness of breath and coughing up blood to sudden death. The mortality rate in this condition is high due to difficulties in a correct diagnosis. To estimate the risk, physicians use Wells score calculator.

  2. Paradoxical embolism - blockage of one of the brain arteries, resulting in a stroke. The severity of a stroke is assessed with the NIH stroke scale calculator. Due to the cardiovascular system's construction, the embolus from the systemic circulation can move to the brain only if a person has a defect in the heart structure, e.g., atrial septum.

VTE risk score in pregnancy or after labor - risk factors for VTE in pregnancy

VTE may cause death in pregnancy and the postpartum period. Its risk rises during pregnancy, reaching the highest after labor.

Why is pregnancy such a significant risk factor for VTE? There are a few reasons, all stemming from the physiological changes in pregnant women:

  • Pelvic venous compression by the growing uterus;
  • Compression of the left iliac vein by the right iliac artery; and
  • Significant changes in pro-and anti-coagulant and fibrinolytic pathways, more prominent than in non-pregnant individuals.

Venous thromboembolism in pregnancy - RCOG risk factors

This VTE risk assessment tool in pregnancy is based on the Royal College of Obstetricians and Gynaecologists (RCOG) recommendations and takes into account three groups of risk factors:

  1. Pre-existing risk factors;
  2. Obstetric risk factors; and
  3. Transient risk factors.

Each of the groups are outlined below. Points assigned to each risk factor for VTE in pregnancy are given in the brackets next to each description.

In the first group, pre-existing risk factors, we may find:

  • Previous VTE, except a single event related to major surgery (4);
  • Previous VTE provoked by major surgery (3);
  • Known high-risk thrombophilia: antithrombin deficiency, protein C or S deficiency, compound or genetically homozygous for low-risk thrombophilias (3);
  • Medical comorbidities e.g. cancer, heart failure, active systemic lupus erythematosus (SLE), inflammatory polyarthropathy or inflammatory bowel disease, nephrotic syndrome, type I diabetes mellitus (DM) with nephropathy, sickle cell disease, or a current intravenous drug user (3);
  • Family history of unprovoked or estrogen-related VTE in a first-degree relative (parent, full sibling, or child) (1);
  • Known low-risk thrombophilia - no VTE: heterozygous for factor V Leiden or prothrombin G20210A mutations (1);
  • Age > 35 years (1);
  • Obesity, for BMI ≥ 30 (1), BMI ≥ 40 (2);
  • Parity ≥ 3 - if you have given birth three times or more to a fetus aged ≥ 24 weeks, regardless if born alive or stillborn (1);
  • Smoker 🚬 (1); and
  • Gross varicose veins (1);

Among the obstetric risk factors there are:

  • Pre-eclampsia in current pregnancy (1);
  • ART/IVF, but only if we assess the risk before giving birth antenatally. ART stands for assisted reproductive technology and IVF - in vitro fertilization (1);
  • Multiple pregnancy 👶👶👶 (1);
  • Caesarean section in labor (2);
  • Elective cesarean section (1);
  • Mid-cavity or rotational operative delivery (1);
  • Prolonged labor, lasting over 24 hours (1);
  • PPH, postpartum bleeding with a need of > 1 liter or transfusion 🩸 (1);
  • Preterm birth < 37+0 weeks in current pregnancy (1); and
  • Stillbirth in current pregnancy (1).

The last group are transient risk factors:

  • Any surgical procedure in pregnancy or puerperium except immediate repair of the perineum, e.g., appendicectomy, postpartum sterilization (3);
  • Hyperemesis (3);
  • OHSS, ovarian hyperstimulation syndrome, only if assessed in the first trimester (4);
  • Current systemic infection 😷 (1); and
  • Immobility, dehydration (1).

All the above factors are needed for the VTE risk assessment in pregnancy, which we use in this calculator.

How to use this VTE risk score calculator in pregnancy?

To calculate VTE risk score in pregnancy, you need to follow these steps:

  1. Choose whether you're pregnant or have just given birth.
  2. Provide your BMI.
  3. Tell us if you're older or younger than 30.
  4. Choose any of the risk factors that apply to you by changing NO to YES.
  5. The result is ready!

The number is the total number of points you received for your answers. This VTE risk score as well as medical examination and overall assessment help physicians make a decision on whether the patient needs prophylaxis.

VTE prophylaxis guidelines

VTE prophylaxis postpartum and in pregnancy may be either pharmacological or mechanical. We described both of them below:

  1. Mechanical:
  • Compression stockings;
  • Intermittent pneumatic compression devices;
  • Calf exercise, "pumping"; and
  • Early ambulation after surgery.
  1. Pharmacological (anticoagulation) 💊:
  • Low molecular weight heparin (LMWH) - The agent of choice for antenatal or postnatal prophylaxis, also safe for breastfeeding;
  • Unfractionated heparin (UFH) - Only in women with a very high risk;
  • Vitamin K antagonists, e.g., warfarin - Restricted to only a few situations during pregnancy, e.g., some women with mechanical heart valves. They are safe to breastfeed with.
  • Direct oral anticoagulants (DOACs) - After a consultation with a hematologist; and
  • Aspirin - Not a recommended VTE treatment in pregnancy or puerperium.

The use of pharmacological prophylaxis doesn't exclude the use of a mechanical one!


What is VTE in pregnancy?

Venous thromboembolism in pregnancy is the formation of blood clots in veins. Pregnant and postpartum women are at increased risk of this process due to venous stasis and hypercoagulability.

The condition is around four to ten times more common in pregnant women than in non-pregnant ones of the same age, so the VTE assessment in pregnancy is crucial. There are multiple risk factors of VTE, including inherited, acquired, and typical for pregnancy.

What does VTE stand for?

VTE is a medical abbreviation for venous thromboembolism. It is a blood clot that starts in a vein and may travel to blood vessels in the lungs or brain.

It occurs in 1 in 100 000 women of fertile age and is between four to ten times more common in pregnancy. In some developed countries, including the UK, it's the leading cause of maternal death, occurring in one-third of deaths.

What are the VTE in pregnancy guidelines?

There are various guidelines for the management of venous thromboembolism in pregnancy, with one of the most well known prepared by the Royal College of Obstetricians and Gynecologists.

As VTE is a condition more likely to affect pregnant women and as a leading cause of maternal death in developed countries, proper prophylaxis and treatment are crucial.

How to treat VTE in pregnancy?

For VTE prophylaxis we have mechanical and pharmacological means of VTE treatment in pregnancy, such as:

  • Compression stockings;
  • Exercises; and
  • Low molecular weight heparin and unfractionated heparin.

It's important to remember, that some agents cannot be given to pregnant women or only under special circumstances, e.g., vitamin K antagonists or prohibited aspirin.

We try our best to make our Omni Calculators as precise and reliable as possible. However, neither we nor our content providers warrant the accuracy of the information on this site. All information on this website is for informational purposes only and is not intended to and should not serve as a substitute for medical consultation, diagnosis or treatment. Please consult your health care provider before making any health care decisions. Omni Calculator and its content providers expressly disclaim responsibility, and shall have no liability, for any damages, loss, injury, or liability whatsoever suffered as a result of your reliance on the information contained in this site. Your use of the site is only your own risk.

Dominika Śmiałek, MD, PhD candidate
am pregnant 🤰
Pre-existing risk factors
Age ≥ 35 years
Previous VTE
Previous VTE provoked by major surgery
High-risk thrombophilia
Family history of unprovoked/estrogen related VTE in first-degree relative
Low-risk thrombophilia
Parity ≥ 3 🧒
Smoker 🚬
Gross varicose veins
Obstetric risk factors
Pre-eclampsia in current pregnancy
Multiple pregnancy 👶👶👶
Transient risk factors
Any surgical procedure in pregnancy or puerperium
OHSS (first trimester only)
Current systemic infection 😷
Immobility, dehydration
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