Approach to Shortness of Breath in a 24-Week Pregnant Patient
Shortness of breath in a 24-week pregnant patient requires careful evaluation to distinguish between physiological changes of pregnancy and pathological conditions, with pulmonary embolism being a critical diagnosis to exclude due to its significant mortality risk.
Initial Assessment
Physiological vs. Pathological Causes
Physiological shortness of breath in pregnancy:
- Normal physiological hyperventilation due to increased progesterone
- Reduced residual capacity and expiratory reserve volume from uterine expansion
- Increased tidal volume due to heightened chemosensitivity to CO₂ and O₂ 1
- May be accompanied by fatigue, reduced exercise tolerance, and orthopnea
Warning signs suggesting pathological causes:
- Persistent excessive shortness of breath that doesn't resolve with rest
- Severe chest pain
- Hypoxemia
- Tachycardia or tachypnea
- Hemoptysis, syncope, unexplained hypotension 2
Diagnostic Approach
History and Physical Examination Focus Points
- Duration and progression of symptoms
- Associated symptoms (chest pain, cough, sweating, hemoptysis)
- Pre-existing conditions (asthma, cardiac disease, thromboembolic risk factors)
- Assess for abnormal alveolar-arterial gradient (>15 mm Hg) 2
- Evaluate for signs of right heart strain or deep vein thrombosis
Initial Testing
Chest radiograph
- First-line imaging study for evaluating shortness of breath
- Low radiation exposure to fetus (negligible risk) 2
Oxygen saturation and arterial blood gases
- Assess for hypoxemia and acid-base status
ECG
- To evaluate for cardiac causes
Further Diagnostic Testing for Suspected Pulmonary Embolism
D-dimer testing is NOT recommended
- Poor specificity (15%) and inadequate sensitivity (73%) in pregnancy
- Documented false negatives in pregnant women with PE 2
Compression ultrasound of lower extremities
- Consider if DVT suspected
- Positive finding may eliminate need for further testing
Imaging for suspected PE:
- Ventilation-perfusion (V/Q) scan or CT pulmonary angiogram (CTPA)
- Choice depends on institutional expertise and patient factors
Management of Specific Conditions
Asthma
- Safe medications during pregnancy:
- Cromoglycic acid and ipratropium
- Short-acting beta-agonists
- Inhaled corticosteroids
- Systemic corticosteroids when necessary 1
- Poorly controlled asthma poses greater risk to fetus than judicious medication use
Pulmonary Embolism
- Immediate anticoagulation if PE confirmed
- Consider specialized interventions for massive or submassive PE
- Multidisciplinary approach involving maternal-fetal medicine 3
Cardiac Causes
- Consider peripartum cardiomyopathy (affects 1:2500-4000 live births)
- Symptoms may mimic asthma or normal pregnancy changes
- Echocardiogram if cardiac cause suspected 4
Safety Precautions
If shortness of breath occurs during physical activity:
- Stop activity immediately and rest
- Avoid physical activity in excessive heat or humidity
- Maintain adequate hydration
- Seek medical attention if symptoms persist 2
Red Flags Requiring Immediate Medical Attention
- Persistent excessive shortness of breath not resolving with rest
- Severe chest pain
- Regular and painful uterine contractions
- Vaginal bleeding
- Persistent dizziness or faintness not resolving with rest 2
Pitfalls to Avoid
- Misattribution bias: Assuming shortness of breath is always physiological in pregnancy
- Diagnostic anchoring: Attributing symptoms to pre-existing conditions (e.g., asthma) without considering other causes 4
- Delayed diagnosis: Failing to re-evaluate if symptoms don't improve with initial treatment
- Radiation concerns: Avoiding necessary imaging due to unfounded radiation fears (properly performed diagnostic tests pose minimal risk to fetus) 2
Remember that pregnant women can develop the same acute conditions as non-pregnant individuals, but with potentially higher morbidity and mortality if diagnosis is delayed.