Severe obstetric morbidity in the United States: 1998-2005.

OBJECTIVE To examine trends in the rates of severe obstetric complications and the potential contribution of changes in delivery mode and maternal characteristics to these trends. METHODS We performed a cross-sectional study of severe obstetric complications identified from the 1998-2005 Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project. Logistic regression was used to examine the effect of changes in delivery mode and maternal characteristics on rates of severe obstetric complications. RESULTS The prevalence of delivery hospitalizations (per 1,000) complicated by at least one severe obstetric complication increased from 0.64% (n=48,645) in 1998-1999 to 0.81% (n=68,433) in 2004-2005. Rates of complications that increased significantly during the study period included renal failure by 21% (from 0.23 to 0.28), pulmonary embolism by 52% (0.12 to 0.18), adult respiratory distress syndrome by 26% (0.36 to 0.45), shock by 24% (0.15 to 0.19), blood transfusion by 92% (2.38 to 4.58), and ventilation by 21 % (0.47 to 0.57). In logistic regression models, adjustment for maternal age had no effect on the increased risk for these complications in 2004-2005 relative to 1998-1999. However, after adjustment for mode of delivery, the increased risks for these complications in 2004-2005 relative to 1998-1999 were no longer significant, with the exception of pulmonary embolism (odds ratio 1.30) and blood transfusion (odds ratio 1.72). Further adjustment for payer, multiple births, and select comorbidities had little effect. CONCLUSION Rates of severe obstetric complications increased from 1998-1999 to 2004-2005. For many of these complications, these increases were associated with the increasing rate of cesarean delivery. LEVEL OF EVIDENCE III.