title: Severe and critical cases of H1N1 influenza in pregnancy: a Chinese perspective.
abstract: BACKGROUND
  In 2009, an outbreak of A/H1N1 influenza spread worldwide. Following the start of winter in Liaoning province in China, the number of pregnant women infected with influenza increased significantly. Some of them developed respiratory failure and multiple organ failure.
  
  
  OBJECTIVE
  The aim of this study was to determine the high-risk factors associated with the development of critical illness in the hospitalized pregnant women with A/H1N1 infection.
  
  
  METHODS
  This retrospective cohort study was carried out in the tertiary care obstetric department of a large general hospital.
  
  
  METHODS
  The clinical data of H1N1 pregnant women hospitalized from November 2009 to January 2010 was reviewed. We classified these cases into severe and critical grades according to H1N1 influenza treatment guidelines. We selected maternal age, gestational age, and the time interval between symptom-onset and hospital admission as related factors of critical illness.
  
  
  METHODS
  Logistic regression analyses to determine the relevance and importance of factors significantly associated with critical illness.
  
  
  RESULTS
  Eighteen cases of H1N1 influenza pregnant women were admitted. Ten pregnant women were severe cases and eight pregnant women were critical cases. The maternal age (OR=0.979, 95% CI: 0.749~1.279)and the time interval between symptom-onset and hospital admission (OR=1.41, 95% CI: 0.917~2.169) were not found to be risk factors for critical cases. The significant risk factor associated with critical illness is gestational age (OR=53.726, 95% CI: 131.165~2477.918). The risk varied by weeks of gestation, with an odds ratio of 1.034 (95% CI: 0.968-1.106) during the first trimester, 9.667 (95% CI: 0.750-124.59) during the second trimester, and 87 (95% CI: 6.750-1121.39) during the third trimester.
  
  
  CONCLUSIONS
  Gestational age is associated with the risk of developing critical infection. The risk increases with increasing weeks of gestation.
authors: Department of Obstetrics and Gynecology, Shengjing Hospital, China Medical University, China.
authors: J
authors: J
authors: Liu
authors: Q
authors: Q
authors: Li
authors: H
authors: H
authors: Cui
authors: C
authors: C
authors: Liu
mesh_terms: D000328:Adult; D002681:China; D005260:Female; D005865:Gestational Age; D006760:Hospitalization; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000145:classification / Q000503:physiopathology*; D008423:Maternal Age; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000145:classification / Q000503:physiopathology* / Q000821:virology; D012307:Risk Factors; D012720:Severity of Illness Index; D013997:Time Factors; D055815:Young Adult