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Thromboembolism in Pregnancy

Practice Essentials

Pregnancy increases the risk of venous thromboembolism (VTE) 4- to 5-fold over that in the nonpregnant state.
The two manifestations of VTE are deep venous thrombosis (DVT) and pulmonary embolus (PE). Although most reports suggest that VTE can occur at any trimester in pregnancy, studies suggest that VTE is more common during the first half of pregnancy (see the image below). Sequelae of DVT and PE include complications such as pulmonary hypertension, post-thrombotic syndrome, and venous insufficiency.

Estimated gestational age at time of diagnosis of

Estimated gestational age at time of diagnosis of antepartum deep venous thrombosis (n=94).

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Signs and symptoms

The signs and symptoms of VTE are nonspecific and common in pregnancy. Diagnosis of VTE by physical examination is frequently inaccurate, even though one study found that 80% of pregnant women with DVT experience pain and swelling of the lower extremity.

Clinical signs and symptoms of PE are rarely encountered together; the classic symptoms are as follows

Dyspnea – 82%

Abrupt onset of chest pain – 49%

Cough – 20%

The most common presenting signs of PE are as follows:




Patients with massive PE may present with the following:



Pulseless cardiac electrical activity


See Clinical Presentation for more detail.


Laboratory studies

D-dimer testing is often used in the diagnosis of DVT in nonpregnant patients due to its high negative predictive value. Pregnancy decreases the specificity of d-dimer testing, however d-dimer retains good negative predictive value in the setting of suspected DVT. Limited data suggests that D-dimer may have lower sensitivity in the setting of suspected PE.

Imaging studies

Imaging for DVT and/or PE is the best means of screening and evaluation for these conditions. The current initial test of choice in the evaluation of VTE is compression ultrasonography (CUS) of the lower extremity veins.

CUS has been shown to be more than 95% sensitive and specific for proximal lower extremity DVT.
CUS is less accurate for the diagnosis of pelvic DVT.
In pregnancy, CUS should be performed with the patient in the left lateral decubitus position and with Doppler analysis of flow variation during respiration to maximize the study’s ability to diagnose pelvic DVT.

However, if the CUS study is equivocal, if Doppler testing is abnormal, or if suspicion of pelvic DVT is high, further evaluation with serial CUS or magnetic resonance imaging (MRI) is recommended.
MRI has been shown to have 97% sensitivity and 95% specificity for pelvic DVT in nonpregnant patients.

Imaging studies used in the diagnosis of PE include the following:

Chest radiography: Recommended prior to the evaluation for PE to determine whether other etiologies may explain the patient’s symptoms (eg, pneumonia, atelectasis, pulmonary edema) and to identify the next appropriate imaging test

Ventilation/perfusion (V/Q) scanning: In a pregnant patient with no known pulmonary disease and a normal chest radiograph, V/Q scanning is the recommended study to evaluate for PE

Spiral computed tomography pulmonary angiography (CT-PA): If the patient has an abnormal chest radiograph, known pulmonary disease, or a non-diagnostic V/Q scan, then spiral CT-PA is recommended

See Workup for more detail.


Once the diagnosis of VTE is made, therapeutic anticoagulation should be initiated in the absence of contraindications. The common classes of anticoagulation drugs are as follows:

Indirect thrombin inhibitors: Include unfractionated heparin and low ̶-molecular-weight heparin (LMWH), as well as synthetic heparin pentasaccharides and orally administered Factor Xa inhibitors (rivaroxaban, apixaban, edoxaban)

Direct thrombin inhibitors: Include argatroban, lepirudin, bivalirudin, dabigatran

Vitamin K antagonist: Warfarin is included in this class

Heparin (unfractionated and low molecular weight) is the preferred drug for managing VTE in pregnancy.

See Treatment and Medication for more detail.

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