Severe and critical cases of H1N1 influenza in pregnancy: A chinese perspective

Context : 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.
Aims : 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.
Settings and Design : This retrospective cohort study was carried out in the tertiary care obstetric department of a large general hospital.
Materials and 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.
Statistical analysis : 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.