Anesthesia-related maternal mortality in the United States: 1979-2002.

OBJECTIVE: To examine 12 years of anesthesia-related maternal deaths from 1991 to 2002 and compare them with data from 1979 to 1990, to estimate trends in anesthesia-related maternal mortality over time, and to compare the risks of general and regional anesthesia during cesarean delivery.

METHODS: The authors reviewed anesthesia-related maternal deaths that occurred from 1991 to 2002. Type of anesthesia involved, mode of delivery, and cause of death were determined. Pregnancy-related mortality ratios, defined as pregnancy-related deaths due to anesthesia per million live births were calculated. Case fatality rates were estimated by applying a national estimate of the proportion of regional and general anesthetics to the national cesarean delivery rate.

RESULTS: Eighty-six pregnancy-related deaths were associated with complications of anesthesia, or 1.6% of total pregnancy-related deaths. Pregnancy-related mortality ratios for deaths related to anesthesia is 1.2 per million live births for 1991-2002, a decrease of 59% from 1979-1990. Deaths mostly occurred among younger women, but the percentage of deaths among women aged 35-39 years increased substantially. Delivery method could not be determined in 14%, but the remaining 86% were undergoing cesarean delivery. Case-fatality rates for general anesthesia were 16.8 per million in 1991-1996 and 6.5 per million in 1997-2002, and for regional anesthesia were 2.5 and 3.8 per million, respectively. The resulting risk ratio between the two techniques for 1997-2002 was 1.7 (confidence interval 0.6-4.6, P=.2).

CONCLUSION: Anesthetic-related maternal mortality decreased nearly 60% when data from 1979-1990 were compared with data from 1991-2002. Although case-fatality rates for general anesthesia are falling, rates for regional anesthesia are rising.

LEVEL OF EVIDENCE: II.