Jamieson DJ, Honein MA, Rasmussen SA, Williams JL, Swerdlow DL, Biggerstaff MS, Lindstrom S, Louie JK, Christ CM, Bohm SR, Fonseca VP, Ritger KA, Kuhles DJ, Eggers P, Bruce H, Davidson HA, Lutterloh E, Harris ML, Burke C, Cocoros N, Finelli L, MacFarlane KF, Shu B, Olsen SJ. Novel Influenza A (H1N1) Pregnancy Working Group. H1N1 2009 influenza virus infection during pregnancy in the USA. The Lancet.* 2009 July. Available at ScienceDirect.*

Summary

Novel H1N1 2009 influenza virus has been identified as the cause of a widespread outbreak of febrile respiratory infection in the United States and worldwide. We summarized cases of infection with novel H1N1 virus in pregnant women identified in the United States during the first month of the present outbreak, and deaths associated with this virus during the first 2 months of the outbreak.

Methods

After initial reports of infection in pregnant women, the Centers for Disease Control and Prevention (CDC) began systematically collecting additional information about cases and deaths in pregnant women in the United States with novel H1N1 virus infection as part of enhanced surveillance. A confirmed case was defined as an acute respiratory illness with laboratory-confirmed novel H1N1 virus infection by real-time reverse-transcriptase PCR or viral culture; a probable case was defined as a person with an acute febrile respiratory illness who was positive for influenza A, but negative for H1 and H3. We used population estimates derived from the 2007 census data to calculate rates of admission to hospital and illness.

Findings

From April 15 to May 18, 2009, 34 confirmed or probable cases of novel H1N1 in pregnant women were reported to CDC from 13 states; 11 (32%) women were admitted to hospital. The estimated rate of admission for novel  H1N1 influenza virus infection in pregnant women during the first month of the outbreak was higher than it was in the general population (0.32 per 100 000 pregnant women, 95% CI 0.13–0.52 vs 0.076 per 100,000 population at risk, 95% CI 0.07–0.09). Between April 15 and June 16, 2009, six deaths in pregnant women were reported to the CDC; all were in women who had developed pneumonia and subsequent acute respiratory distress syndrome requiring mechanical ventilation.

Interpretation

Pregnant women might be at increased risk for complications from novel H1N1 virus infection. These data lend support to the present recommendation to promptly treat pregnant women with H1N1 influenza virus infection with anti-influenza drugs.

 

Related Resources

Podcast: In pregnant women with suspected H1N1, treat promptly! A conversation with Denise Jamieson of the CDC.*

 

*

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Page last reviewed: 8/3/09
Page last modified: 8/3/09
Content source: Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion