Asthma exacerbations during the first trimester of pregnancy and the risk of congenital malformations among asthmatic women

Background: Uncontrolled maternal asthma during pregnancy has been hypothesized as a cause of congenital malformation, but literature is scare on this topic. Objective: The aim of this study was to investigate whether asthmatic women who had an exacerbation during the first trimester of pregnancy were more at risk of having a baby with a congenital malformation. Methods: From the linkage of 3 Canadian administrative databases, we reconstructed a cohort of 4344 pregnancies of asthmatic women. Asthma exacerbations were assessed during the first trimester of pregnancy and were defined as a filled prescription for oral corticosteroids, an emergency department visit, or a hospitalization for asthma. Congenital malformations were assessed at birth and during the first year of life of the newborn by using diagnoses recorded in the databases. Generalized estimating equation models were used to estimate adjusted odds ratios of congenital malformations in association with asthma exacerbations. Results: In the cohort we identified 398 (9.2%) babies with at least 1 malformation and 261 (6.0%) with a major malformation. The crude prevalences of malformations were 12.8% and 8.9%, respectively, for women who had and those who did not have an exacerbation. The adjusted odds ratio for all malformations was 1.48 (95% CI, 1.04-2.09) when comparing women who had and those who did not have an exacerbation. The corresponding figures were 1.32 (95% CI, 0.86-2.04) for major malformations. Conclusion: Asthma exacerbations during the first trimester of pregnancy were found to significantly increase the risk of a congenital malformation.