Antiviral medication use in a cohort of pregnant women during the 2009-2010 influenza pandemic

Preventing influenza-like illness (ILI) during pregnancy with antiviral medication use (AVMU) can mitigate serious health risks to mother and foetus. We report on AVMU in pregnant women in Ontario, Canada, and describe characteristics of AVMU during the 2009-2010 H1N1 pandemic. Rates and risk estimates of AVMU were compared across multiple categories and stratified across ILI infection status. Increased AVMU was observed in women with influenza infections, active smokers, those vaccinated against influenza, and those with pre-existing co-morbidities. Decreased AVMU was observed in women with multiple gestations, and those in neighbourhoods of high immigrant concentrations. Our stratified analysis indicated that the observed patterns differed by ILI infection status. We demonstrated that once infected, women across multiple groups were equally likely to use antiviral medications. In this report we also propose possible clinical explanations for the observed differences in AVMU, which will be useful in planning prevention initiatives for future pandemics.