Influenza-like illness among Hong Kong Chinese pregnant women.

We assessed the self-reported prevalence of influenza-like illness (ILI) during pregnancy in two samples of 546 and 2764 new mothers who were pregnant during the 2009-10 and 2010-11 peak influenza seasons. During pregnancy, 11% of participants experienced an ILI. Cough, sore throat and nasal congestion were the most common reported symptoms. Only 4.6% and 9% of the participants in sample 1 and 2 had an underlying chronic illness, respectively, and 3.3% of mothers in both groups were smokers. Conducting regular surveillance on influenza prevalence during pregnancy is essential to evaluate the costs and benefits of influenza vaccination programmes.