Open Access Highly Accessed Research article

Clinical features and risk factors for severe and critical pregnant women with 2009 pandemic H1N1 influenza infection in China

Peng-jun Zhang1, Xiao-li Li1, Bin Cao1, Shi-gui Yang2, Li-rong Liang1, Li Gu1, Zhen Xu3, Ke Hu4, Hong-yuan Zhang5, Xi-xin Yan6, Wen-bao Huang7, Wei Chen8, Jing-xiao Zhang9, Lan-juan Li2*, Chen Wang10* and for the National Influenza A Pandemic (H1N1) 2009 Clinical Investigation Group of China

Author Affiliations

1 Beijing Chao-Yang Hospital, Beijing Institute of Respiratory Medicine, Beijing Key Laboratory of Respiratory and Pulmonary Circulation Disorders, Department of Respiratory Medicine, Capital Medical University, Beijing, China

2 State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, School of Medicine, Zhejiang University, Key Laboratory of Infectious Diseases Key Laboratory of Infectious Diseases, Zhejiang University, Hangzhou, China

3 Disease Control and Emergency Response Office, Chinese Center for Disease Control and Prevention, Beijing, China

4 Renmin Hospital of Wuhan University, Wuhan, China

5 The First Affiliated Hospital of Anhui medical university, Hefei, China

6 Department of Respiratory, Second Hospital of Hebei Medical University, Shi Jiazhuang, China

7 Hang zhou No.1 People's hospital, Hangzhou, China

8 Shengjing Hospital of China Medical University, Shenyang, China

9 the Second Affiliated Hospital, Nanchang University, Changchun, China

10 Department of Respiratory Medicine, Capital Medical University, Beijing Institute of Respiratory Medicine, Beijing Key Laboratory of Respiratory and Pulmonary Circulation Disorders, Beijing Hospital, Ministry of Heath, Beijing, China

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BMC Infectious Diseases 2012, 12:29  doi:10.1186/1471-2334-12-29

Published: 1 February 2012



2009 pandemic H1N1 (pH1N1) influenza posed an increased risk of severe illness among pregnant women. Data on risk factors associated with death of pregnant women and neonates with pH1N1 infections are limited outside of developed countries.


Retrospective observational study in 394 severe or critical pregnant women admitted to a hospital with pH1N1 influenza from Sep. 1, 2009 to Dec. 31, 2009. rRT-PCR testing was used to confirm infection. In-hospital mortality was the primary endpoint of this study. Univariable logistic analysis and multivariate logistic regression analysis were used to investigate the potential factors on admission that might be associated with the maternal and neonatal mortality.


394 pregnant women were included, 286 were infected with pH1N1 in the third trimester. 351 had pneumonia, and 77 died. A PaO2/FiO2 ≤ 200 (odds ratio (OR), 27.16; 95% confidence interval (CI), 2.64-279.70) and higher BMI (i.e. ≥ 30) on admission (OR, 1.26; 95% CI, 1.09 to 1.47) were independent risk factors for maternal death. Of 211 deliveries, 146 neonates survived. Premature delivery (OR, 4.17; 95% CI, 1.19-14.56) was associated neonatal mortality. Among 186 patients who received mechanical ventilation, 83 patients were treated with non-invasive ventilation (NIV) and 38 were successful with NIV. The death rate was lower among patients who initially received NIV than those who were initially intubated (24/83, 28.9% vs 43/87, 49.4%; p = 0.006). Septic shock was an independent risk factor for failure of NIV.


Severe hypoxemia and higher BMI on admission were associated with adverse outcomes for pregnant women. Preterm delivery was a risk factor for neonatal death among pregnant women with pH1N1 influenza infection. NIV may be useful in selected pregnant women without septic shock.

Pregnant women; Neonate; Pandemic H1N1 influenza; Mortality; Non-invasive ventilation