Please cite this paper as: Lim M, Chong C, Tee W, Lim W, Chee J. Influenza A/H1N1 (2009) infection in pregnancy—an Asian perspective. BJOG 2010;117:551–556.

Objective  To describe the characteristics of an obstetric population with influenza A/H1N1 (2009) infection, with a focus on the need for hospitalisation and complications.

Design  Cohort study.

Setting  Tertiary referral centre.

Population  Two hundred and eleven pregnant women with influenza A/H1N1 (2009) infection diagnosed by nasopharyngeal swab polymerase chain reaction (PCR).

Methods  Obstetric patients presenting to our centre were recruited and followed up. Data collected included demographic and clinical information.

Main outcome measures  H1N1 and pregnancy complications, and hospitalisation needs.

Results  The median age of the cohort was 29.0 years (range 16–42 years), the median gestation at referral was 23.0 weeks (range 4–38 weeks), the median time interval between illness onset and presentation was 2.0 days (range 1–7 days), and the median time interval between illness onset and commencement of oseltamivir was 2.0 days (range 1–11 days). Hospital admission was significantly associated with the presence of co‐morbidity (OR 4.14, 95% CI 1.82–9.37, P = 0.0001), breathlessness (OR 5.2, 95% CI 2.19–12.41, P = 0.0003) and sore throat (OR 0.35, 95% CI 0.16–0.73, P = 0.005). There were two cases of pneumonia complicating H1N1 infection, but no mortality. Nine cases developed pregnancy complications. All women recovered.

Conclusions  The need for hospitalisation was significantly associated with breathlessness and co‐morbidity. There was minimal morbidity and no mortality observed. We attribute this to early presentation, diagnosis and treatment.