Association between the timing of asthma diagnosis and medication use during pregnancy

To assess whether asthma medication use during pregnancy differs in women newly diagnosed with asthma early in pregnancy (first 19 weeks of pregnancy) compared to those newly diagnosed up to 2 years pre-pregnancy.

A retrospective population-based cohort study.

To conduct this study, we used the Quebec Asthma and Pregnancy Database (QAPD) constructed by linking two administrative health databases from the province of Quebec (Canada): the Régie de l'Assurance Maladie du Québec and Maintenance et Exploitation des Données pour l'Étude de la Clientèle Hospitalière databases.

A cohort comprising pregnant women newly diagnosed with asthma at any time in the 2 years prior to pregnancy or during the first 19 weeks of pregnancy was selected from the QAPD.

We assessed the number of filled prescriptions of inhaled corticosteroids (ICS), ICS/long-acting β2 agonists (LABA), and short-acting β2 agonists (SABA), as well as the number of days' supply of oral corticosteroid (OCS) from the 20^th week of pregnancy until delivery. Poisson regression was used to compare the rates of asthma medication use in women diagnosed pre-pregnancy versus early in pregnancy. The cohort included 1731 women newly diagnosed with asthma pre-pregnancy and 359 women newly diagnosed with asthma early in pregnancy. Women diagnosed early in pregnancy were more likely to use ICS (adjusted rate ratio: 1.9, 95% confidence interval (CI): 1.6-2.3) and SABA (adjusted rate ratio: 2.0, 95% CI: 1.7-2.4) from the 20th week of pregnancy until delivery than those newly diagnosed pre-pregnancy. No significant differences were observed in the use of ICS/LABA [adjusted rate ratio: 0.9, 95% CI: 0.7-1.3] and OCS [adjusted rate ratio: 0.8, 95% CI: 0.6-1.2].

The higher use of ICS and SABA observed in women newly diagnosed with asthma early in pregnancy may suggest a more persistent asthma phenotype caused by pregnancy-triggered hormonal changes.