Background Evaluation of the severity of the pregnant women with suitable admission to the Intensive Care Unit (ICU)is very important for obstetricians.By now there are no criteria for critically ill obstetric patients admitted to the ICU.In this article,we investigated the admission criteria of critically ill patients admitted to the ICU in order to provide a referral basis of reasonable use of the ICU.Methods A retrospective analysis of critically ill pregnant women admitted to the ICU in Perking University Third Hospital in China in the last 6 years (from January 2006 to December 2011) was performed,using acute physiology and chronic health evaluation Ⅱ (APACHE-Ⅱ),Marshall and WHO near miss criteria to assess the severity of illness of patients.Results There were 101 critically ill pregnant patients admitted to the ICU.Among them,25.7％ women were complicated with intal or surgical diseases,and 23.8％ women were patients of postpartum hemorrhage and 23.8％ women were patients of pregnancy-induced hypertension.Sixty-nine cases (68.3％) were administrated with adjunct respiration with a respirator.Sixteen cases (15.8％) required 1-2 types of vasoactive drugs.Fifty-five cases (54.5％)required a hemodynamic monitoring.Seventy-three cases (72.3％) had multiple organ dysfunctions (MODS).The average duration in ICU was (7.5±3.0) days.A total of 12.9％,23.8％ and 74.3％ of women were diagnosed as critically ill according to the APACHE-Ⅱ,Marshall and WHO near miss criteria,respectively.The rate was significantly different according to the three criteria (P＜0.01).Conclusions The WHO near miss criteria can correctly reflect the severity of illness of pregnant women,and the WHO near miss criteria are appropriate for admission of critically ill pregnant women to ICU in China.