1153. Pregnancy as a risk factor for severe outcomes from influenza virus infection: a systematic review and meta-analysis of observational studies
Session: Poster Abstract Session: Public Health
Friday, October 9, 2015
Room: Poster Hall
  • 1153 SR Pregnancy ID Week.pdf (56.8 kB)
  • Background: Pregnancy is widely considered to be an important risk factor for severe complications following influenza infection. As a consequence, WHO recommendations prioritize pregnant women over other risk groups for influenza vaccination. The risk associated with pregnancy has however not been systematically quantified. 

    Methods: Search of MEDLINE, EMBASE, CINAHL, and CENTRAL to identify comparative observational studies (cohort, case-control, cross-sectional and ecological studies) reporting on outcomes of interest in pregnant women with evidence of influenza virus infection compared to non-pregnant patients. Outcomes included pneumonia, hospital admission, admission to intensive care units (ICU), receipt of mechanical ventilatory support, death, and a composite of ICU admission and/or death. A random effects model was used to obtain risk estimates. 

    Results: A total of 148 non-ecological and 10 ecological studies of pregnant women with evidence of influenza virus infection were included. There was a higher risk for influenza-associated hospital admission in pregnant versus non-pregnant patients in meta-analysis (odds ratio (OR) 2.94, 95% confidence interval 1.58-5.47). Meta-analysis found no effect of pregnancy on other influenza-associated outcomes:  mortality (OR 1.03, 0.81-1.3), pneumonia (OR 1.80, 0.72-4.49), receipt of mechanical ventilatory support (OR 1.21, 0.70-2.08), or the composite of ICU admission and/or death (OR 0.95, 0.59-1.67). Influenza-associated ICU admission was less common in pregnant women when compared to non-pregnant women of reproductive age, only (OR 0.51, 0.42-0.62). In ecological studies, 4 of 8 studies reported higher mortality rates, 4 of 4 studies found higher hospital admission rates, and 2 of 2 studies found a higher admission rate to ICUs among pregnant women.

    Conclusion: Meta-analysis of non-ecological studies demonstrated a higher risk of influenza-associated hospital admission for pregnant women, but no increase in other severe influenza events. In contrast, some ecological studies suggested a higher risk of death and ICU admission. Given the limitations of ecological study designs, influenza virus infection in pregnancy may not be associated with severe outcomes other than a higher likelihood of hospital admission.

    Dominik Mertz, MD, MSc1, Johanna Geraci, MSc1, Judi Winkup, MSc1, Justin Ortiz, MD2 and Mark Loeb, MD, MSc, FSHEA1, (1)McMaster University, Hamilton, ON, Canada, (2)World Health Organization, Geneva, Switzerland


    D. Mertz, None

    J. Geraci, None

    J. Winkup, None

    J. Ortiz, None

    M. Loeb, None

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