Pulmonary Function Tests in Pregnancy
Yes, pulmonary function tests (PFTs) can be safely performed during pregnancy and are recommended when clinically indicated, particularly for monitoring women with chronic respiratory conditions like cystic fibrosis and asthma.
Clinical Indications and Safety
PFTs are routinely used during pregnancy without contraindication. The European Respiratory Society guidelines specifically recommend regular monitoring of lung function in pregnant women with cystic fibrosis, with clinic visits at least monthly during the first and second trimesters 1. Similarly, spirometry is commonly used to assess and monitor lung function during pregnancy and serves as a useful tool to monitor maternal health 2.
Specific Applications
Monitoring Chronic Respiratory Disease
- Women with cystic fibrosis should undergo regular lung function monitoring throughout pregnancy, with FEV₁ measurements used to guide clinical management and predict outcomes 1.
- Higher pre-pregnancy FEV₁ values are associated with better pregnancy outcomes and complete return of lung function postpartum 1.
- Pregnant women with asthma benefit from periodic spirometry assessments to optimize disease management during gestation 2.
Expected Physiological Changes
Normal pregnancy causes predictable alterations in pulmonary function parameters:
- FVC (forced vital capacity) decreases progressively with advancing gestation, declining approximately 0.07% per week 2.
- FEV₁ shows variable changes depending on underlying respiratory status, with decreases noted in women without asthma but relative stability in well-controlled asthmatics 2.
- Expiratory reserve volume (ERV) and functional residual capacity (FRC) decrease during pregnancy due to upward displacement of the diaphragm by the gravid uterus 3.
- Flow-volume loop characteristics and closing volume remain unaltered during pregnancy 3.
Practical Considerations
Testing Methodology
Standard spirometry techniques can be used during pregnancy with minor modifications:
- Upright sitting is the most comfortable position for testing during pregnancy, particularly in later trimesters 1.
- Avoid supine positioning, especially during second and third trimesters, to minimize pressure from the gravid uterus on the inferior vena cava 1.
- Cardiopulmonary exercise testing can be performed when indicated, though pregnancy-specific adjustments to protocols should be considered 4.
Clinical Interpretation
A common pitfall is misinterpreting normal pregnancy-related changes as pathology:
- Recognize that decreases in FVC and ERV are physiological adaptations, not necessarily indicative of restrictive lung disease 5, 6, 3.
- Serial measurements are more valuable than single assessments for detecting true pathological changes versus normal gestational variation 2.
- In women with asthma, advancing gestation may actually oppose negative effects on lung function when asthma is optimally managed 2.
Monitoring Frequency
For women with chronic respiratory disease:
- Monthly PFTs during first and second trimesters, increasing to every 2 weeks or more frequently as necessary 1.
- More frequent monitoring is recommended for those with more severe disease (FEV₁ <50% predicted) 1.
Clinical Value
Continuous monitoring of pulmonary function during pregnancy provides significant clinical benefits: