What is the best initial approach for a 28-week pregnant patient with mild shortness of breath (SOB) on exertion, normal exam, and no prior medical conditions?

Reassurance is Appropriate for Mild Exertional Dyspnea at 28 Weeks in a Medically Healthy Pregnant Woman

For a 28-week pregnant patient with mild shortness of breath on exertion, normal physical examination, and no prior medical conditions, reassurance is the appropriate initial approach without pulmonary function testing. 1

Physiologic Basis for Dyspnea in Normal Pregnancy

Pregnancy causes predictable respiratory changes that commonly manifest as exertional dyspnea:

• Reduced residual capacity and expiratory reserve volume occur due to the enlarging uterus displacing the diaphragm upward 2
• Increased tidal volume results from elevated progesterone levels and enhanced chemosensitivity to CO2 and O2 2
• Physiologic hyperventilation is a normal adaptation that many women perceive as shortness of breath 2
• These changes are most pronounced in the third trimester when this patient presents 2

When Pulmonary Function Testing is NOT Indicated

The British Journal of Sports Medicine guidelines clarify that pulmonary function testing is reserved for specific populations:

• Severe respiratory disorders requiring PFTs include: COPD (GOLD 3 or 4), severe asthma (FEV₁ <60% with daily oral corticosteroids), cystic fibrosis (FEV₁ <50%), or restrictive lung disease (FEV₁ <60%) 1
• This patient has none of these conditions and is described as "medically free" 1
• Women with well-controlled mild-moderate respiratory disease who are asymptomatic should be encouraged to maintain physical activity without restriction 1

Critical Red Flags That Would Change Management

While reassurance is appropriate here, you must remain vigilant for features suggesting pathologic causes:

• Cardiac causes: Raised jugular venous pressure, bibasal crepitations, cardiac murmur, or peripheral edema suggest peripartum cardiomyopathy or unmasked cardiac disease 3, 4, 5
• Pulmonary hypertension: Progressive dyspnea with signs of right heart failure requires urgent specialist referral 4, 6
• Severe respiratory disease: Oxygen desaturation with exertion, uncontrolled symptoms, or exercise intolerance below normal pregnancy thresholds 1

Common Pitfall to Avoid

The most dangerous error is assuming all dyspnea in pregnancy is physiologic without proper examination. 3 If symptoms worsen or fail to improve with reassurance and activity modification, you must revisit the diagnosis and consider cardiac causes, particularly peripartum cardiomyopathy, which can initially mimic asthma or normal pregnancy symptoms 3. The European Heart Journal emphasizes that shortness of breath wrongly ascribed to pregnancy itself can delay diagnosis of mitral stenosis or pulmonary hypertension 1.

Appropriate Counseling for This Patient

• Explain that mild exertional dyspnea is normal at 28 weeks gestation due to mechanical and hormonal changes 2
• Encourage continued physical activity as tolerated, as pregnant women without contraindications should maintain moderate-vigorous physical activity 1
• Provide return precautions: Instruct her to seek immediate care if she develops chest pain, severe dyspnea at rest, palpitations, syncope, or signs of fluid overload 1
• Schedule routine follow-up to reassess symptoms and ensure no progression 1