When should pulmonary embolism (PE) be suspected in a pregnant woman?

When to Suspect Pulmonary Embolism in Pregnant Women

Clinicians must maintain a high index of suspicion for PE in pregnant women and rely primarily on clinical judgment, as many normal pregnancy symptoms overlap with PE presentation and no validated clinical prediction rules exist for this population. 1

Primary Clinical Presentations

The most common features that should trigger suspicion for PE in pregnant women include:

• Dyspnea (62% of confirmed cases) - particularly if severe or of acute onset, as mild breathlessness is common in normal pregnancy 1
• Pleuritic chest pain (55% of confirmed cases) - sharp, localized chest pain that worsens with breathing 1
• Tachycardia - elevated heart rate beyond what is expected in normal pregnancy 1
• Hypoxemia - documented low oxygen saturation 1
• Cough (24% of confirmed cases) 1

Additional Warning Signs

Suspect PE when pregnant women present with:

• Hemoptysis - coughing up blood 1
• Syncope - sudden loss of consciousness 1
• Unexplained hypotension - low blood pressure without clear cause 1
• Abnormal alveolar-arterial gradient (>15 mm Hg) - found in 58% of pregnant women with confirmed PE 1
• PaO₂ <65 mm Hg - significantly low arterial oxygen 1

Critical Diagnostic Challenges

No individual clinical feature or combination of features has been shown to reliably predict PE in pregnancy. A study of 304 pregnant and postpartum women found no significant risk association between any clinical features (chest pain, dyspnea, desaturation, tachycardia, increased A-A gradient, PaO₂ <65 mm Hg) and the presence of PE. 1

Key Pitfalls to Avoid

• Do not dismiss symptoms as "normal pregnancy" - mild subjective shortness of breath, tachycardia, and leg edema can accompany both normal pregnancy and PE, making differentiation difficult 1
• Do not rely on D-dimer to exclude PE - D-dimer has only 73% sensitivity in pregnancy with false negatives documented in confirmed PE cases 1
• Maintain suspicion even with normal vital signs - PaO₂ is normally maintained during pregnancy (though may be lower in supine position during third trimester) 1

High-Risk Clinical Contexts

Be particularly vigilant for PE in pregnant women with:

• Prior venous thromboembolism - strongest risk factor 1
• Postpartum period (especially first 6 weeks) - highest risk period, particularly after Caesarean section 1, 2
• Obesity 1
• Medical comorbidities (cardiac, cerebrovascular, renal disorders) 1
• Pregnancy complications - stillbirth, pre-eclampsia, postpartum hemorrhage, placenta previa, polyhydramnios, chorioamnionitis 1
• Leg symptoms suggesting DVT - unilateral leg swelling, pain, warmth 1, 3

Practical Approach

When any suspicion arises, proceed directly to formal diagnostic assessment rather than attempting to "rule out" PE clinically. 1, 3 The American Thoracic Society emphasizes that clinicians must generally rely on clinical judgment and employ a high index of suspicion, as the consequences of missing PE (maternal death) far outweigh the risks of diagnostic imaging. 1

The prevalence of confirmed PE among investigated pregnant women is only 2-7%, reflecting appropriate low thresholds for investigation rather than overdiagnosis. 1, 4 This low yield is acceptable given PE remains a leading cause of pregnancy-related maternal death in developed countries. 1, 5