Diagnostic Approach for Pulmonary Embolism in Pregnant Patients

Clinical Assessment and Initial Approach

The American Thoracic Society recommends that clinicians maintain a high index of suspicion for pulmonary embolism (PE) in pregnant women, as normal pregnancy can mimic some PE symptoms, and D-dimer testing should not be used to exclude PE due to its poor specificity and inadequate sensitivity during pregnancy 3, 4
Pregnant women with suspected PE commonly present with shortness of breath, pleuritic chest pain, hypoxemia, and tachycardia 3, 4
There are no validated clinical prediction rules specifically for determining pre-test probability of PE in pregnant patients, highlighting the need for a high index of suspicion 3, 4

The American College of Chest Physicians recommends that in pregnant women with suspected PE and signs/symptoms of deep venous thrombosis (DVT), perform bilateral venous compression ultrasound (CUS) of lower extremities 1, 2
If CUS is positive, initiate anticoagulation treatment, and if CUS is negative, proceed to chest radiography 1, 2
For all pregnant women with suspected PE, chest radiography (CXR) should be the first radiation-associated procedure, which helps triage between lung scintigraphy and CT pulmonary angiography (CTPA) 2, 5

If CXR is normal, perform lung scintigraphy (V/Q scan) rather than CTPA, as V/Q scanning delivers lower radiation dose to maternal breast tissue and is more likely to yield diagnostic results 2, 5
If CXR is abnormal, perform CTPA rather than lung scintigraphy, as CTPA provides better diagnostic yield and can identify alternative diagnoses 2, 5

Technically inadequate CTPA studies occur in 6-36% of pregnant women, primarily due to suboptimal vascular opacification and respiratory motion artifacts, and repeat CTPA after a non-diagnostic study should be undertaken cautiously 7
For unstable patients or when studies are not available promptly, empiric anticoagulation should be considered while awaiting diagnostic results, as recommended by the American Heart Association 8, 7

CTPA delivers higher radiation dose to maternal breast tissue compared to V/Q scanning, with a lifetime relative risk of radiation-induced breast cancer in a 25-year-old woman undergoing a single CTPA estimated at 1.011, according to the National Cancer Institute 2