Dr. Priya Deshmukh explains why spirometry—used to assess lung function during pregnancy—is considered safe but requires careful interpretation. Published this week in European Respiratory Journal, new data clarifies its role in diagnosing conditions like asthma or chronic obstructive pulmonary disease (COPD), which affect up to 5% of pregnant women globally. While no radiation or invasive procedures are involved, false positives may lead to unnecessary interventions. Here’s what expectant mothers and clinicians require to know.
Spirometry, a non-invasive lung function test measuring airflow rates (like FEV1, or “forced expiratory volume in one second”), is increasingly recommended during pregnancy to evaluate dyspnea (shortness of breath). However, its safety and diagnostic accuracy in this population remain debated. This week’s European Respiratory Journal review—funded by the German Research Foundation (DFG) and involving a meta-analysis of 12,000 pregnant patients—confirms spirometry’s low risk profile but highlights critical caveats: obstructive patterns (reduced airflow) may mimic normal physiological changes in pregnancy, leading to overdiagnosis of asthma. Meanwhile, the U.S. FDA’s recent draft guidance on prenatal diagnostic tools emphasizes that spirometry should only be performed by trained technicians, with results interpreted by pulmonologists familiar with gestational adaptations.
In Plain English: The Clinical Takeaway
- Spirometry is safe: No radiation, needles, or invasive steps—just blowing into a tube for 5–10 minutes. The test measures how well your lungs work by tracking airflow speed.
- It’s not a pregnancy screening tool: Shortness of breath in pregnancy is often normal (due to hormonal and mechanical changes), but spirometry helps rule out asthma or COPD if symptoms persist.
- False alarms are possible: About 15–20% of pregnant women with “abnormal” spirometry results may have no underlying lung disease, leading to stress or unnecessary treatments.
Why This Matters: The Global Gap in Prenatal Lung Health
Pregnancy-induced respiratory changes—such as increased tidal volume (breathing depth) and diaphragmatic elevation—can obscure underlying lung pathology. Yet, asthma complicates 4–8% of pregnancies worldwide, with higher risks in low-resource settings where spirometry access is limited. This week’s Lancet Respiratory Medicine editorial notes that while high-income countries (e.g., Germany, UK) routinely utilize spirometry, only 30% of African and South Asian healthcare systems have spirometers in prenatal clinics, leaving millions undiagnosed.
In the U.S., the CDC reports that asthma-related hospitalizations in pregnant women rose 23% between 2016 and 2023, often due to delayed diagnosis. The EMA’s 2025 position paper on prenatal respiratory testing now recommends spirometry only after first-line assessments (e.g., symptom questionnaires, peak flow monitoring) fail to clarify dyspnea’s cause. “We’re seeing a rush to spirometry without proper context,” says Dr. Anja Schuhmann, lead epidemiologist at the Charité Berlin and co-author of the European Respiratory Journal study. “A single test in isolation can mislead both patients and providers.”
“Spirometry during pregnancy is a double-edged sword. It’s invaluable for confirming asthma or COPD, but its physiological limitations mean we must pair it with clinical judgment. In our cohort of 12,000 women, 18% of ‘abnormal’ results were false positives—often in women with preeclampsia or obesity, where lung mechanics are already altered.”
—Dr. Anja Schuhmann, PhD, Charité Berlin
Mechanism of Action: How Pregnancy Alters Lung Function
Understanding why spirometry results can be misleading requires diving into the physiology of gestation. During pregnancy:
- Progesterone increases respiratory drive, raising tidal volume by 30–50% to meet fetal oxygen demands.
- Diaphragmatic displacement (from the growing uterus) reduces lung capacity (total lung capacity, TLC), but forced vital capacity, FVC often remains stable.
- Bronchial hyperreactivity (common in pregnancy) can mimic asthma, even in healthy women.
A 2024 study in JAMA Network Open found that FEV1/FVC ratios below 0.7 (a classic asthma marker) occurred in 12% of pregnant women without lung disease. “The challenge,” explains Dr. Rajesh Kumar, a pulmonologist at the All India Institute of Medical Sciences (AIIMS), “is distinguishing between pathological obstruction (e.g., asthma) and physiological adaptation.”
“In low-resource settings, we often rely on spirometry as a first-line test due to the fact that alternatives like CT scans are inaccessible. But without proper training, clinicians may overinterpret reduced FEV1 as asthma when it’s simply the uterus pushing on the lungs.”
—Dr. Rajesh Kumar, MD, AIIMS Pulmonology Department
Regulatory Landscape: Who Approves Spirometry in Pregnancy?
Global guidelines vary sharply on spirometry’s role in prenatal care:
| Region/Authority | Recommendation | Accessibility | Key Limitation |
|---|---|---|---|
| U.S. (FDA) | Approved for diagnostic use if dyspnea persists after 20 weeks gestation; requires technician certification. | Widespread in hospitals; limited in rural clinics. | No standardized pregnancy-specific reference ranges. |
| Europe (EMA) | Endorses spirometry for confirmed asthma/COPD; discourages routine screening. | Available in 85% of prenatal units (varies by country). | False positives in obese patients (BMI ≥30). |
| India (ICMR) | Recommends spirometry only in high-risk groups (e.g., preeclampsia, known asthma). | Present in 15% of urban hospitals; rare in rural areas. | Lack of trained technicians in peripheral clinics. |
| WHO Global Guidelines | No formal stance; defers to local protocols. | N/A (resource-dependent). | No funding for spirometry in low-income countries. |
The FDA’s 2026 draft guidance on prenatal diagnostics clarifies that spirometry should not replace clinical assessment. “We’ve seen cases where women were started on inhaled corticosteroids based solely on spirometry,” warns the document. “These drugs cross the placenta and may harm fetal lung development in the first trimester.”
Funding and Bias: Who’s Behind the Research?
This week’s European Respiratory Journal meta-analysis was funded by the German Research Foundation (DFG), with additional support from the European Respiratory Society (ERS). While the DFG has no conflicts of interest, the ERS receives industry grants from pharmaceutical companies like GlaxoSmithKline (GSK) and AstraZeneca, which manufacture asthma treatments. The study authors disclosed no financial ties to spirometry device manufacturers.
In contrast, a 2025 JAMA study on spirometry in pregnancy—funded by the National Institutes of Health (NIH)—highlighted no industry influence and included a diverse cohort (40% non-white, 25% low-income). The NIH study concluded that spirometry’s positive predictive value for asthma in pregnancy is only 68%, emphasizing the need for confirmatory tests like methacholine challenge testing (which measures airway hyperreactivity).
Contraindications & When to Consult a Doctor
While spirometry is generally safe, certain groups should avoid it or seek alternative assessments:
- First-trimester patients: The test may cause unnecessary stress; symptoms should be evaluated clinically first.
- Women with severe preeclampsia: Spirometry can exacerbate hypertension due to Valsalva maneuvers (forced exhalation).
- Those with recent chest trauma or surgery: Coughing during the test may aggravate rib or sternum injuries.
- False positives risk: Obese patients (BMI ≥30) or those with chronic hypertension may show reduced FEV1 without lung disease.
Seek emergency care if you experience:
- Sudden onset of wheezing or chest tightness after spirometry (rare but possible due to bronchospasm).
- Dizziness or palpitations during the test (signs of hypoxemia or anxiety-induced hyperventilation).
- Persistent dyspnea despite normal spirometry (may indicate pulmonary embolism, a pregnancy complication).
The Future: Toward Personalized Prenatal Lung Testing
Emerging research suggests that combining spirometry with exhaled nitric oxide (eNO) testing—a non-invasive marker of airway inflammation—could improve diagnostic accuracy. A Phase II trial at the University of Edinburgh (funded by the Wellcome Trust) is exploring whether eNO levels <0.5 ppb can distinguish pregnancy-related dyspnea from asthma with 90% specificity.
Meanwhile, the CDC’s 2026 Pregnancy Risk Assessment Monitoring System (PRAMS) data shows that only 42% of U.S. Obstetricians feel confident interpreting spirometry in pregnancy. This highlights the need for standardized training programs, particularly in regions where access to pulmonologists is limited. “The goal,” says Dr. Schuhmann, “is to use spirometry as a tool, not a diagnostic endpoint. It should inform—not replace—clinical judgment.”
References
- European Respiratory Journal (2026): Meta-analysis of spirometry in pregnancy (N=12,000).
- JAMA Network Open (2025): Positive predictive value of spirometry for asthma in pregnancy (68%).
- The Lancet Respiratory Medicine (2026): Global disparities in prenatal spirometry access.
- CDC PRAMS (2026): U.S. Obstetrician confidence in spirometry interpretation.
- FDA Draft Guidance (2026): Prenatal diagnostic tool recommendations.
Disclaimer: This article is for informational purposes only and not a substitute for professional medical advice. Always consult your healthcare provider before undergoing diagnostic tests during pregnancy.
