Relationship between changes in inhaled corticosteroid use and markers of uncontrolled asthma during pregnancy

Study objective: To describe changes in inhaled corticosteroid use during pregnancy and markers of uncontrolled asthma, and to evaluate the association between them.

Design: Population-based, cross-sectional study.

Data source: Three administrative claims databases in Québec, Canada.

Patients: A cohort of 4434 asthmatic women (4920 pregnancies) who delivered their infants between 1990 and 2002 and who used inhaled corticosteroids before their pregnancy.

Measurements and main results: The average daily doses of inhaled corticosteroids during pregnancy and during the 9 months before conception were compared; the change in use was categorized as discontinuation (reduction of ≥75%), reduction (26-75% reduction), no change (±25% change), or increase (increase of ≥25%). The markers of uncontrolled asthma included at least one asthma exacerbation and the use of three or more doses/week of a short-acting β(2) -agonist during pregnancy. Generalized estimating equation models were used for statistical analyses. In nearly 50% of the pregnancies (2388 [48.5%] of 4920), the women either stopped or reduced their doses of corticosteroid during pregnancy, and these doses were already quite low before pregnancy. The proportion of women who had an asthma exacerbation during pregnancy was 8.2% among women who discontinued corticosteroids and greater than 20% in all of the other groups. All of the groups used frequent doses of short-acting β(2) -agonists. Discontinuing inhaled corticosteroid use during pregnancy was associated with a lower risk of exacerbations (odds ratio [OR] 0.42, 95% confidence interval [CI] 0.33-0.54), whereas increasing inhaled corticosteroid use was associated with a higher risk (OR 1.42, 95% CI 1.17-1.72), compared with no change in use.

Conclusion: Because of residual confounding by asthma severity, our study was not able to show that women who stopped inhaled corticosteroids during pregnancy were at increased risk of having an asthma exacerbation. However, women who stopped corticosteroids tended to have a milder form of asthma, which is reassuring and suggests that women can recognize, to a certain extent, the need to continue taking their controller agents if necessary.