Background: We performed a large population-based cohort study to investigate whether maternal use of different dosing of inhaled corticosteroids during the first trimester of pregnancy for the treatment of asthma increases the risk of congenital malformations in the offspring.
Methods: From the linkage of three administrative Canadian databases we reconstructed a cohort of 4,561 pregnancies from asthmatic women who delivered between 1990 and 2000. A two-stage sampling cohort design was used to acquire additional data from the woman’s medical chart. Cases of congenital malformation were identified from the medical services database or the hospital database. Using refill patterns of medications, we calculated the average daily dose of inhaled corticosteroids used during the first trimester and categorized it as follow: 0, 1-500, 500-1000, 1000 g per day in beclomethasone-CFC equivalent. A Generalized Estimation Equation model was used to estimate the adjusted odds ratio of congenital malformation as a function of ICS daily dose. All analyses were performed for all malformations and major malformations separately.
Results: Within the cohort we identified 418 babies with a congenital malformation (9.2%) and 278 of those had a major malformation. Close to 40% of women used inhaled corticosteroids during the first trimester, but only 5.3% of women used more than 500 g per day. The adjusted odds ratio for all malformations associated with inhaled corticosteroids use during the first trimester were: 0.77 (95% CI: 0.53-1.13) for 1- 500, 0.41 (95% CI: 0.19-0.92) for 501-1000 and 1.00 (95% CI: 0.42-2.36) for more than 1000 g per day. The corresponding figures for major malformations were 0.90 (95% CI: 0.64-1.24), 0.56 (95% CI: 0.22-1.43) and 1.67 (95% CI: 0.56-5.03).
Conclusion: This study adds evidence to the safety of inhaled corticosteroids for the treatment of asthma during pregnancy, in regards to the likelihood of congenital malformation.
- Congenital malformations
- Inhaled corticosteroids
- cohort study