What is the diagnosis and treatment plan for a 37-year-old pregnant woman at 38 weeks of gestation with shortness of breath (dyspnea) and no significant medical history?

Differential Diagnosis and Immediate Assessment

In a 37-year-old woman at 38 weeks gestation presenting with shortness of breath, pulmonary embolism must be immediately excluded as it remains the leading cause of pregnancy-related maternal death, occurring in 1 per 1,000-3,000 deliveries. 1, 2

Critical Red Flags Requiring Immediate Workup

Assess immediately for the following high-risk features that mandate urgent PE evaluation:

• Severe dyspnea at rest (versus exertional dyspnea only) 1, 2
• Pleuritic chest pain 1, 2
• Syncope or presyncope 2
• Hemoptysis 1, 2
• Unexplained hypotension or tachycardia 1, 2
• Oxygen desaturation (SpO2 <95%) 2
• Respiratory rate >35/min (absolute indication for ICU transfer) 1
• Unilateral leg swelling (suggests DVT) 2

Diagnostic Algorithm

Step 1: Initial Assessment

• Measure vital signs including oxygen saturation and respiratory rate - SpO2 should be maintained >95% 1
• Perform focused physical examination looking for tachypnea (>20 breaths/min at rest), abnormal lung sounds, unilateral leg swelling, and signs of cardiopulmonary compromise 2

Step 2: If High Clinical Suspicion for PE

• Initiate empiric anticoagulation immediately while diagnostic workup proceeds in hemodynamically stable patients with high clinical suspicion 1
• Bilateral lower extremity compression ultrasound first - if DVT is detected, treatment can begin without further radiation exposure 1, 2
• Arterial blood gas in upright position (supine position can falsely lower PaO2 by up to 2 kPa in late pregnancy; abnormal A-a gradient >15 mm Hg present in 58% of pregnant women with confirmed PE) 1
• Chest X-ray to help risk-stratify, though normal results do not exclude PE 2

Step 3: If No Red Flags Present

If physical examination is completely normal with no oxygen desaturation, no tachypnea at rest, no chest pain, and mild exertional dyspnea only, this likely represents physiologic adaptation to pregnancy 2

Treatment Plan

If PE is Confirmed or Highly Suspected:

• Oxygen supplementation to maintain SpO2 >95% (pregnant patients develop hypoxemia rapidly due to decreased functional residual capacity and increased oxygen demand) 1
• Anticoagulation as per standard PE protocols 1
• Multidisciplinary team involvement mandatory including obstetric anesthesia, obstetrics, cardiology, pulmonology, and intensive care for unstable patients 1

If Physiologic Dyspnea (Normal Exam, No Red Flags):

• Reassurance is appropriate for mild exertional dyspnea with normal physical examination 2
• Encourage continued moderate-vigorous physical activity - patients should not restrict activity 2
• Patient education to return immediately if developing chest pain, severe dyspnea at rest, palpitations, syncope, or signs of fluid overload 2

Alternative Diagnoses to Consider:

• Subtle cardiac dysfunction - pregnancy may unmask myocardial dysfunction; consider echocardiography if symptoms are significant and persistent, as pregnant women with SOB may show increased septal thickness, shorter E-wave deceleration time, and higher pulmonary artery pressures 3
• Aspiration pneumonitis - can occur even outside active labor or anesthesia administration 4
• Pulmonary edema - consider if risk factors present (preeclampsia, fluid overload, cardiac disease) 5

Key Clinical Pitfall

The hypercoagulable state of pregnancy increases PE risk throughout gestation, and symptoms may be subtle. Do not dismiss dyspnea as "normal pregnancy changes" without systematically excluding life-threatening causes first. 2 The threshold for investigation should be low given that PE is the leading cause of maternal death in developed countries. 1, 2