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Epidemiology and clinical outcomes of hospitalizations for acute respiratory or febrile illness and laboratory-confirmed influenza among pregnant women during six influenza seasons, 2010-2016

Dawood FS, Garg S, Fink RV, Russell ML, Regan AK, Katz MA, Booth S, Chung H, Klein NP, Kwong JC, Levy A, Naleway A, Riesel D, Thompson MG, Wyant BE, Fell DB; PREVENT workgroup. J Infect Dis. 2020; 221(10):1703-12. Epub 2019 Dec 26. DOI:

Background — Pregnant women are at increased risk of seasonal influenza hospitalizations, but data about the epidemiology of severe influenza among pregnant women remain largely limited to pandemics.

Methods — To describe the epidemiology of hospitalizations for acute respiratory infection or febrile illness (ARFI) and influenza-associated ARFI among pregnant women, administrative and electronic health record data were analyzed from retrospective cohorts of pregnant women hospitalized with ARFI who had testing for influenza viruses by RT-PCR in Australia, Canada, Israel and the United States during 2010-2016.

Results — Of 18,048 ARFI-coded hospitalizations, 1,064 (6%) included RT-PCR testing for influenza viruses, of which 614 (58%) were influenza-positive. Of 614 influenza-positive ARFI hospitalizations, 35% were in women with low socioeconomic status, 20% with underlying conditions, and 67% in their third trimesters. The median length of influenza-positive hospitalizations was 2 days (IQR 1-4), 18% (95% confidence interval (CI) 15-21%) resulted in delivery, 10% (95% CI 8-12%) included a pneumonia diagnosis, 5% (95% CI 3-6%) required intensive care, 2% (95% CI 1-3%) included a sepsis diagnosis, and <1% (95% CI 0-1%) resulted in respiratory failure.

Conclusions — Our findings characterize seasonal influenza hospitalizations among pregnant women and can inform assessments of the public health and economic impact of seasonal influenza on pregnant women.

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