Incidence of New Asthma in Pregnancy and Associated Risk Factors: A 10-Year Nationwide Population-Based Study.

Pregnancy is a risk factor for asthma exacerbation and may trigger new-onset asthma in nonasthmatics. This study evaluated the epidemiology of newly diagnosed asthma during pregnancy and the associated risk factors among previously nonasthmatic women. Twelve-year medical data from the Korean National Health Insurance claims database (from January 2007 to December 2018) of Korean women who gave birth between January 2012 and December 2015 were collected. Previously nonasthmatic women were defined as those who had not been diagnosed with asthma for at least 4 years before pregnancy. Asthma flare-up was defined as asthma diagnosed three times or more and treated at least once with an oral corticosteroid. A nested case-control study was performed, and then the derived risk factors were applied to whole study population. Among the nonasthmatic women, 7.5% experienced asthma during pregnancy including episodes requiring hospitalization and 18.6% of them visited emergency room. Older age, primiparity, multi-fetal pregnancy, and rhinitis were identified as the risk factors. Among the entire study population, moderate to severe rhinitis was a significant risk factor across all age groups, while primiparity with multi-fetal pregnancy was one for older pregnant women; 22.7% in those ≥ 34 years old experienced asthma flare-ups compared to only 3.5% in the < 34 age group. A substantial portion of pregnant women with no history of asthma experienced an asthma flare-up during pregnancy. Multi-fetal pregnancy as primiparity at a later age and moderate to severe rhinitis are risk factors for the new development of asthma.