SAN DIEGO—In 1993, a working group of the National Asthma Education and Prevention Program (NAEPP) established guidelines for managing asthma during pregnancy, with treatment to be based on the asthma severity classifications of mild, moderate, or severe. However, the classification scheme was developed without a precise understanding of the relationship between these categories and actual gestational asthma morbidity. Moreover, it was intended for pregnant asthmatic patients not receiving asthma treatment.

A recent study in the Journal of Allergy and Clinical Immunology describes an alternative classification system that addresses both concerns.[1] Modifying the standard NAEPP classifications of asthma to include medication use, the researchers showed that asthma morbidity during pregnancy can indeed be closely predicted by the patient’s initial asthma severity classification; the new classifications were validated in both untreated and treated pregnant patients.

Michael Schatz, MD, the lead investigator, said that physicians should use the modified categories of asthma severity to classify their pregnant patients, primarily because his group’s findings suggested that women with more severe asthma may not be receiving adequate controller therapy. “Persistent asthma,” he emphasized, “should be aggressively treated during pregnancy, with adequate control assured by frequent follow-up using both subjective and objective measures of pulmonary function.”

The study took place at 16 centers of the National Institute of Child Health and Human Development–Maternal Fetal Medicine Units Network and included 1,739 obstetric patients with physician-diagnosed asthma. The women, all of whom were less than 26 weeks pregnant at enrollment, were assigned to one of the three asthma severity categories and monitored for exacerbations (defined as symptoms severe enough to result in medical intervention). Information on exacerbations was collected prospectively each month and analyzed as a function of asthma severity.

A woman’s asthma morbidity during pregnancy was strongly correlated with her initial level of disease severity. Women who had mild asthma (no regular medication use, symptoms on fewer than three days per week, FEV1 more than 80% of predicted) were thus less likely to experience exacerbations than were the women with moderate asthma (daily use of medications other than oral corticosteroids, symptoms on more than two days per week, or FEV1 within 60% to 80% of predicted), and these women in turn were less likely to have exacerbations than were the women with severe asthma (regular oral corticosteroid use or FEV1 less than 60% of predicted); exacerbation rates in the three groups were 12.6%, 25.7%, and 51.9%, respectively.

Asthma symptoms during labor and delivery, tracked as present or absent, followed a similar trend, rising from 13.3% to 21.0% to 46.2% as asthma severity increased from mild to moderate to severe.

Among patients with sufficient symptom data at the end of the pregnancy to have their asthma severity regraded, 30% of those who initially had mild asthma were reclassified as having either moderate or severe disease because their symptoms had worsened. Conversely, 23% of those who initially had moderate or severe asthma experienced improvement in symptoms, and thus their disease was reclassified as mild.

Regular use of asthma medication during pregnancy appeared to influence the classification of asthma severity. The researchers compared outcomes in the 700 patients whose asthma was classified as moderate based on NAEPP criteria (symptoms and spirometric results) with that in the 114 patients whose disease would have been classified as mild under the NAEPP system but who were classified as moderate based on their need for daily medication (as per the study protocol). Surprisingly, rates of asthma exacerbations were similar in the groups. One can speculate, Dr. Schatz said, that “adequately controlled moderate-severe asthma and mild asthma would lead to similar morbidity during pregnancy.”

—Verna L. Schwartz, MS