Effect of Pregnancy on Quantitative Medication Use and Relation to Exacerbations in Asthma

BACKGROUND: The quantification of asthma medication reduction and its relation to an aggravation of asthma during pregnancy at an individual level are unclear. METHODS: We conducted a nationwide retrospective cohort study of asthmatic pregnant women in South Korea. All of the asthma medications were ranked from 1 to 4 according to the guideline-based stepwise approach. We assessed the daily sums of the ranks of the asthma medications and their association with exacerbations during three phases based on the individual's delivery date: before, during, and after pregnancy. RESULTS: The study cohort included 115,169 asthmatic pregnant women who gave birth between 2011 and 2013. The subjects were clustered into four groups according to the daily rank sums of their asthma medication. Asthma medications were rapidly reduced at the beginning of the pregnancy and then slowly increased after delivery. Exacerbations were more frequent in the group with higher rank-sum values than in the group with lower values. Overall exacerbations were reduced during pregnancy compared to before or after delivery. CONCLUSIONS: Asthmatic pregnant women tended to reduce their asthma medication use during pregnancy. This led to a greater number of exacerbations in a small part of the study population.