Clinical features and outcomes of peripartum obstetric patients admitted to the intensive care unit: A nationwide inpatient database in Japan

BACKGROUND: Pregnant and postpartum women face an increasing risk of severe complications due to pathophysiological changes, advanced maternal age, obesity, and reproductive technologies. Globally, maternal mortality remains a critical concern, with numerous critically ill obstetric patients requiring intensive care each year. However, comprehensive nationwide data on obstetric intensive care unit (ICU) admissions in Japan remain scarce. This study aimed to provide a detailed analysis of the clinical characteristics, causes of ICU admission, interventions, and outcomes of obstetric patients in Japan using a large, nationwide inpatient database. METHODS: This retrospective observational study utilized the Japanese Diagnosis Procedure Combination inpatient database, which encompasses more than 90% of tertiary emergency hospitals, covering the period from July 2010 to March 2022. We included patients who were admitted to the ICU and delivered either during hospitalization or within one week before hospital admission. Patient demographics, comorbidities, causes of ICU admission, interventions, and clinical outcomes (e.g., in-hospital mortality) were analyzed. Comparative analyses were conducted between survivors and non-survivors to identify key differences in clinical presentation and outcomes. RESULTS: A total of 8,184 obstetric patients from 195 institutions were admitted to ICUs during the study period. The median age was 34 years (interquartile range, 30-38), and 53.2% underwent cesarean delivery. Hemorrhage was the most common cause of ICU admission (52.6%), followed by hypertensive disorders of pregnancy (16.7%). Major interventions included blood transfusions in 71.5% of patients, mechanical ventilation in 28.0%, and transcatheter arterial embolization in 18.0%. Overall in-hospital mortality was 1.1%. Compared with survivors, non-survivors had a lower proportion of hemorrhage-related cases but exhibited a higher prevalence of amniotic fluid embolism, cardiovascular and cerebrovascular disease, infection, pulmonary disease, trauma, and suicide. CONCLUSIONS: This nationwide study highlights hemorrhage as the primary cause of obstetric ICU admissions in Japan, with an all cause in-hospital mortality of 1.1%. These findings highlight the need for targeted interventions to enhance maternal care, optimize ICU resource allocation, and improve outcomes among critically ill obstetric patients. TRIAL REGISTRATION: This was a retrospective observational study and was not registered prospectively as trial registration is not applicable to this type of study.