Asthma morbidity during pregnancy can be predicted by severity classification.

Background: The 1993 National Asthma Education Program Working Group on Asthma and Pregnancy defined asthma severity as mild, moderate, or severe on the basis of symptoms and spirometry, but no studies have evaluated the relationship between this classification system and subsequent asthma morbidity during pregnancy.

Objective: The objective of this study was to evaluate the relationship between asthma severity classification during pregnancy and gestational asthma exacerbations.

Methods: Asthma severity was defined according to the 1993 classification, adjusted to include medication requirements, in a volunteer sample of 1739 pregnant asthmatic patients who were less than 26 weeks' gestation.

Results: Initial asthma classification (mild, moderate, or severe) was significantly related to subsequent asthma morbidity during pregnancy (hospitalizations, unscheduled visits, corticosteroid requirements, and asthma symptoms during labor and delivery). Exacerbations during pregnancy occurred in 12.6% of patients initially classified as mild, 25.7% of patients classified as moderate, and 51.9% of patients classified as severe (P <.001). Asthma morbidity was similar, whether patients were classified as moderate or severe by symptoms and spirometry or by medication requirement. Thirty percent of initially mild patients were reclassified as moderate-severe during pregnancy, and 23% of the initially moderate-severe patients were reclassified as mild later in pregnancy; asthma morbidity in these patients changed accordingly.

Conclusion: The National Asthma Education Program Working Group on Asthma and Pregnancy classification of asthma severity, adapted to include medication use, predicts subsequent asthma morbidity during pregnancy.