Pregnancy, asthma and exacerbations: a population-based cohort

Background Asthma exacerbations during pregnancy are associated with adverse maternal and perinatal outcomes. Identifying modifiable risk factors are essential for improving health outcomes. We aimed to describe exacerbation patterns during pregnancy and identify exacerbation risk factors, particularly modifiable risk factors such as inhaled corticosteroid (ICS) use. Methods A cohort study using UK primary care and hospital data (2004–2020) to identify pregnant women with asthma. Exacerbations were defined as a short course of oral corticosteroids, emergency department visit, or unscheduled hospital admission. Multivariable logistic regression was used to assess associations between maternal characteristics and exacerbations (primary outcome) and ICS use (secondary outcome). Results Among 40 196 pregnant women with asthma, total exacerbations declined by ∼30% during pregnancy. However, exacerbations associated with hospital admission increased by 30–45% during the second and third trimesters, declining abruptly after delivery. ICS prescriptions were reduced in 31% of women during pregnancy. Decreased ICS use was associated with suboptimal asthma control pre-pregnancy, age, ethnicity and smoking. The strongest exacerbation risk factors were a history of exacerbations (adjusted-OR, 95% CI: 4.09, 3.81–4.39), reduced ICS during pregnancy (2.29, 2.12–2.47) and ≥4 prescriptions/year for ICS+another-preventer before pregnancy (2.11, 1.87–2.37). Additional risk factors included blood eosinophilia, smoking and obesity. Conclusions Despite fewer total exacerbations, exacerbations associated with a hospital admission increased during pregnancy. One-third of women reduced ICS use during pregnancy, yet this was the second largest exacerbation risk factor, and completely modifiable. Other major risk factors were type-2 inflammation and another modifiable risk factor, suboptimal asthma control pre-pregnancy.