Pregnancy as a risk factor for severe influenza infection: An individual participant data meta-analysis

Dominik Mertz, Calvin Ka Fung Lo, Lyubov Lytvyn, Justin R. Ortiz, Mark Loeb, Li Wei Ang, Mehta Asmita Anlikumar, Isabelle Bonmarin, Victor Hugo Borja-Aburto, Heinz Burgmann, Jordi Carratalà, Gerardo Chowell, Catia Cilloniz, Jessica Cohen, Jeffery Cutter, Laurent Filleul, Shikha Garg, Steffen Geis, Melissa Helferty, Wan Ting HuangSeema Jain, Biljana Joves Sevic, Paul Kelly, Gabriela Kusznierz, Nicola Lehners, Luana Lenzi, Ivan T. Ling, Robyn Mitchell, Siobhain A. Mulrennan, Sergio A. Nishioka, Robert Norton, Won Sup Oh, Pablo Orellano, Wolfgang Poeppl, Roberto Pontarolo, Odette Popovici, Alejandro Rodriquez, Bettina Schlehe, Paul Schnitzler, Bunyamin Sertogullarindan, Yuelong Shu, Geoffrey Taylor, Deborah L. Thompson, Antoni Torres, Arianne B. Van Gageldonk-Lafeber, Diego Viasus, Quanyi Wang, Cuiling Xu

Research output: Contribution to journalOriginal Articlepeer-review

62 Scopus citations


Background: WHO identifies pregnant women to be at increased risk for severe outcomes from influenza virus infections and recommends that they be prioritized for influenza vaccination. The evidence supporting this, however, is inconsistent. Ecologic studies in particular suggest more severe outcomes from influenza infection during pregnancy than studies based on individual patient data. Individual studies however may be underpowered and, as reported in a previous systematic review, confounding factors could not be adjusted for. We therefore conducted an individual participant data meta-analysis to assess the risk for severe outcomes of influenza infection in pregnant women while adjusting for other prognostic factors. Methods: We contacted authors of studies included in a recently published systematic review. We pooled the individual participant data of women of reproductive age and laboratory confirmation of influenza virus infection. We used a generalized linear mixed model and reported odds ratios (OR) and 95% confidence intervals (CI). Results: A total of 33 datasets with data on 186,656 individuals were available, including 36,498 eligible women of reproductive age and known pregnancy status. In the multivariable model, pregnancy was associated with a 7 times higher risk of hospital admission (OR 6.80, 95%CI 6.02-7.68), among patients receiving medical care as in- or outpatients, pregnancy was associated with a lower risk of admission to intensive care units (ICU; OR 0.57, 95%CI 0.48-0.69), and was not significantly associated with death (OR 1.00, 95%CI 0.75-1.34). Conclusions: Our study found a higher risk of influenza associated hospitalization among pregnant women as compared to non-pregnant women. We did not find a higher mortality rate or higher likelihood of ICU admission among pregnant women who sought medical care. However, this study did not address whether a true community based cohort of pregnant women is at higher risk of influenza associated complications.

Original languageAmerican English
Article number683
JournalBMC Infectious Diseases
Issue number1
StateIndexed - 2 Aug 2019

Bibliographical note

Publisher Copyright:
© 2019 The Author(s).


  • Influenza
  • Meta-analysis
  • Pregnancy
  • Severity
  • Vaccine


Dive into the research topics of 'Pregnancy as a risk factor for severe influenza infection: An individual participant data meta-analysis'. Together they form a unique fingerprint.

Cite this