It is generally known that pregnancy in asthmatic patients increases the risk of asthma exacerbations and poor perinatal outcomes. However, the effect of pregnancy in asthmatic patients on health care use is not known well. In addition, its effect on perinatal outcomes is still controversial because of study limitations caused by ethical issues. National Health Insurance claim data are an ideal resource for studying real-world health care use patterns of asthma.

We sought to evaluate the effect of pregnancy on asthma in terms of asthma-related health care use and prescription patterns in concert with the effect of asthma exacerbations on adverse pregnancy outcomes.

Among all asthmatic patients in the Korean National Health Insurance claim database from January 2009 to December 2013, pregnant women who delivered in 2011 with pre-existing asthma were enrolled. Analyses included asthma-related health care use and prescription patterns compared between pregnant asthmatic women and nonpregnant female asthmatic control subjects, as well as within the pregnant subjects from before pregnancy throughout postpartum periods. In addition, the association between asthma exacerbation during pregnancy and adverse pregnancy outcomes was assessed.

A total of 3,357 pregnant asthmatic patients were compared with 50,355 nonpregnant asthmatic patients, and 10,311 pregnant patients were included to determine the effect of asthma exacerbations on adverse pregnancy outcome in the study. Pregnant asthmatic patients underwent more asthma-related hospitalizations (1.3% vs 0.8%, P = .005) but had significantly fewer outpatient visits and prescriptions for most asthma medications than nonpregnant asthmatic patients. The proportion of patients ever hospitalized gradually increased throughout pregnancy (first trimester, 0.2%; second trimester, 0.5%; and third trimester, 0.7%; P = .018). The prevalence of asthma exacerbation during pregnancy was 5.3%, and the patients who had acute exacerbation during pregnancy had significantly higher asthma-related health care use in terms of hospitalization, intensive care unit admission, and emergency department and outpatient visits within 1 year before delivery than those who had not. However, asthma exacerbation during pregnancy was not significantly related to adverse perinatal outcomes, except for cesarean section (27.1% vs 18.9%, P < .001). All exacerbations were managed with systemic corticosteroids, and the patients who ever experienced acute exacerbations maintained asthma medications, including inhaled corticosteroid–based inhalers, throughout the pregnancy period.

Pregnancy profoundly affects asthma-related health care use but to a different degree depending on whether the patient experienced an exacerbation. Asthma exacerbation during pregnancy is not associated with adverse pregnancy outcomes while managed appropriately with systemic corticosteroids. However, further studies are needed to clarify the effect of asthma control on perinatal outcome and delivery method.