• Rachel Holstein, Fatimah S Dawood, Alissa O'Halloran, Charisse Cummings, Dawud Ujamaa, Daily KirleyPamPCalifornia Emerging Infections Program, Oakland, California (P.D.K.)., Kimberly Yousey-Hindes, Emily Fawcett, Maya L Monroe, Sue Kim, Ruth Lynfield, Chelsea McMullen, Alison Muse, Nancy M Bennett, Laurie M Billing, Melissa Sutton, Ann Thomas, H Keipp Talbot, William Schaffner, Ilene Risk, Carrie Reed, and Shikha Garg.
• Centers for Disease Control and Prevention, Atlanta, Georgia (R.H., F.S.D., A.O., C.C., C.R., S.G.).
• Ann. Intern. Med. 2022 Feb 1; 175 (2): 149158149-158.

BackgroundPregnant women may be at increased risk for severe influenza-associated outcomes.ObjectiveTo describe characteristics and outcomes of hospitalized pregnant women with influenza.DesignRepeated cross-sectional study.SettingThe population-based U.S. Influenza Hospitalization Surveillance Network during the 2010-2011 through 2018-2019 influenza seasons.PatientsPregnant women (aged 15 to 44 years) hospitalized with laboratory-confirmed influenza identified through provider-initiated or facility-based testing practices.MeasurementsClinical characteristics, interventions, and in-hospital maternal and fetal outcomes were obtained through medical chart abstraction. Multivariable logistic regression was used to evaluate the association between influenza A subtype and severe maternal influenza-associated outcomes, including intensive care unit (ICU) admission, mechanical ventilation, extracorporeal membrane oxygenation, or in-hospital death.ResultsOf 9652 women aged 15 to 44 years and hospitalized with influenza, 2690 (27.9%) were pregnant. Among the 2690 pregnant women, the median age was 28 years, 62% were in their third trimester, and 42% had at least 1 underlying condition. Overall, 32% were vaccinated against influenza and 88% received antiviral treatment. Five percent required ICU admission, 2% required mechanical ventilation, and 0.3% (n = 8) died. Pregnant women with influenza A H1N1 were more likely to have severe outcomes than those with influenza A H3N2 (adjusted risk ratio, 1.9 [95% CI, 1.3 to 2.8]). Most women (71%) were still pregnant at hospital discharge. Among 754 women who were no longer pregnant at discharge, 96% had a pregnancy resulting in live birth, and 3% experienced fetal loss.LimitationMaternal and fetal outcomes that occurred after hospital discharge were not captured.ConclusionOver 9 influenza seasons, one third of reproductive-aged women hospitalized with influenza were pregnant. Influenza A H1N1 was associated with more severe maternal outcomes. Pregnant women remain a high-priority target group for vaccination.Primary Funding SourceCenters for Disease Control and Prevention.

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