Does pregnancy affect spirometry for diagnosing asthma and is there a gestational age cutoff when spirometry should be avoided?

Spirometry in Pregnancy for Asthma Diagnosis

Spirometry can be safely performed throughout pregnancy for asthma diagnosis and monitoring, with no specific gestational age cutoff when it should be avoided. 1

Effects of Pregnancy on Spirometry and Asthma

• Pregnancy can cause changes in asthma severity, with approximately one-third of women experiencing improved symptoms, one-third unchanged symptoms, and one-third worsened symptoms during pregnancy 1
• Asthma symptoms tend to be relatively stable during the first trimester and last month of pregnancy, with increased symptoms and medication needs more common during the second and third trimesters 1
• Specific phenotypes, such as allergic or eosinophilic asthma, may be more likely to worsen during pregnancy, with rhinitis serving as an indicator of potential worsening 1
• Overweight or obese pregnant women experience asthma exacerbations twice as frequently as healthy-weight pregnant women with asthma 1

Diagnostic Approach for Asthma During Pregnancy

• Spirometry is the preferred method for objective assessment of lung function in pregnant women with suspected asthma 1, 2
• For initial diagnosis, spirometry is preferable to peak expiratory flow (PEF) measurement 1
• For routine follow-up monitoring after diagnosis, either spirometry or PEF measurement is generally sufficient 1
• Additional diagnostic tests that can support asthma diagnosis during pregnancy include:
  • Fractional exhaled nitric oxide (FeNO) measurement 2
  • Blood eosinophil count 2
  • Asthma Control Test (ACT), which has been validated for use in pregnant women 3

Safety of Spirometry During Pregnancy

• There is no evidence suggesting spirometry should be avoided at any specific gestational age during pregnancy 1
• Spirometry is a non-invasive test that does not expose the fetus to radiation, making it safe throughout pregnancy 1, 2
• The benefits of accurate asthma diagnosis and management during pregnancy outweigh any theoretical risks of performing spirometry 4

Importance of Asthma Management During Pregnancy

• Uncontrolled asthma during pregnancy increases risks of:
  • Pre-term birth 1
  • Low birthweight 1
  • Small for gestational age infants 1
  • Pre-eclampsia 1
  • Gestational diabetes 1
  • Perinatal mortality 1, 4
• Active asthma management during pregnancy reduces these risks 1, 4
• Monthly monitoring of asthma symptoms and lung function is recommended throughout pregnancy 1, 4
• Serial ultrasound examinations starting at 32 weeks gestation may be considered for patients with suboptimally controlled asthma and for women with moderate to severe asthma 1

Common Pitfalls to Avoid

• Avoiding diagnostic testing due to unfounded concerns about safety during pregnancy, which can lead to poor asthma control 4, 5
• Failing to objectively measure lung function, which can result in under-treatment of asthma 4
• Not recognizing that asthma severity can change during pregnancy, requiring adjustment of management strategies 1
• Overlooking the importance of treating comorbidities that can worsen asthma control during pregnancy, such as rhinitis, obesity, and viral infections 1, 5

In conclusion, spirometry is a safe and valuable diagnostic tool for assessing asthma throughout pregnancy, with no specific gestational age cutoff when it should be avoided. Regular monitoring of lung function is essential for optimal maternal and fetal outcomes.