Pregnant women with persistent asthma are at a greater risk for worsening symptoms during the course of their pregnancy than women with intermittent asthma, according to a study published in the August 2003 Journal of Allergy and Clinical Immunology (JACI).

Patients who experience asthma symptoms, such as coughing or wheezing, two times a week, or have evidence of airway obstruction between their asthma episodes, have persistent asthma. Those with intermittent asthma have symptoms that occur less that once a week and have a normal lung function between episodes.

The 1993 National Asthma Education and Prevention Program (NAEPP) Working Group on Asthma and Pregnancy defined asthma as mild, moderate and severe based on history of asthma symptoms and measurements of lung function. However, the definitions were designed for untreated patients and there is insufficient data as to how to classify pregnant women already in treatment for their asthma.

Michael Schatz, Kaiser-Permanente Medical Center in San Diego and colleagues wanted to determine the risk of asthma symptoms getting worse during the course of pregnancy by evaluating the original severity classification and adjusting it to include medication use by the patient. Researchers collected information on asthma exacerbations throughout the pregnancy of 1,739 patients.

They then compared the patient's medical records prior to the study with the information collected to determine the risk of their symptoms getting worse. An asthma exacerbation was defined as symptoms severe enough to result in medical intervention, including hospitalizations, unscheduled visits, or prescription of oral corticosteroids.

The frequency of asthma hospitalizations, unscheduled visits, oral steroid use, and symptoms during labor and delivery were significantly lower in subjects whose asthma condition remained mild throughout pregnancy. There was also a significant difference in patients with initially moderate or severe asthma whose conditions were reclassified as mild at the end of pregnancy.

After adjusting for medication use, the study suggests that pregnant asthmatic patients on daily asthma medications should be classified as having moderate asthma. Also, patients requiring regular oral corticosteroids should be classified as having severe asthma. The study's findings suggest that tailoring treatment on the basis of these definitions would reduce the rate of asthma exacerbations during pregnancy.