Clinical description of cohort 3570 severe or critical cases were screened and 394 cases involved pregnant women ( Figure 1 ). Demographic characteristics, underlying conditions, symptoms, and lab findings of the 394 pregnant women are illustrated in diseases were rare in this analysis. None of the patients had been immunized against seasonal influenza or 2009 pH1N1. The median APACHE II score was 7.0 (IQR, [4] [5] [6] [7] [8] [9] [10] [11] . At the time of admission, 351 patients (90.0%) had pneumonia with an abnormal chest radiography or chest computed tomography. The most common symptoms were cough (372; 94.7%) and dyspnoea (199; 50.6%). The median PaO 2 /FiO 2 on admission was 154.7 (IQR, 89.5-320.5) ( Table 1 ). Of the 394 hospitalized patients, 246 (63.7%) were admitted to an ICU at a median of 8 days from onset of illness (IQR 5 to 14; Table 2 ).