OBJECTIVE:

To estimate pregnancy-related mortality caused by seasonal influenza in the United States for comparison with the current 2009 influenza A H1N1 pandemic.

METHODS:

Pregnancy-related deaths were identified in the US Centers for Disease Control and Prevention's (CDC) Pregnancy Mortality Surveillance System (PMSS) database for the years 1998–2005. PMSS collects de-identified copies of vital records supplied by all 50 states, the District of Columbia, and New York City for women who died during or within 1 year after pregnancy. Records in the database broadly classified under deaths due to respiratory infections were identified, and the corresponding archived death certificates were individually reviewed to classify the cause of death as pneumonia or influenza.

RESULTS:

Between 1998 and 2005, 4,693 pregnancy-related deaths were reported to CDC. Of these, 78 women died from influenza or pneumonia; 40 of these deaths occurred during an influenza season. Nearly 75% of deaths occurred during or within 2 weeks of the end of the pregnancy.

CONCLUSION:

On average, five possible influenza-related deaths among pregnant women were reported per year before the emergence of pregnancy-related deaths due to the current H1N1 pandemic compared with the 28 laboratory-confirmed, pregnancy-related deaths reported for the first 4 months of the 2009 pandemic. This highlights the excess mortality among pregnant women resulting from this pandemic influenza virus.

LEVEL OF EVIDENCE:

III

Pregnancy-related deaths due to 2009 influenza A (H1N1) during the first months of the pandemic exceeded the expected yearly deaths caused by seasonal influenza.