Maternal mortality surveillance in the United States: moving into the twenty-first century. 
Although maternal mortality (MM) in the United States declined remarkably during the 20th century, little progress has been made during the last 20 years.  The earlier, historic decline was spurred largely by medical and technological advances, and interest and concern at the local, state, and federal levels led to the development of systems for identifying, reviewing, and analyzing cases of MM.  Organized surveillance systems have determined causation, identified gaps in services, and disseminated findings and recommendations.  Although risks for pregnant women are now low, variability in the risk of death by race, ethnicity, and maternal age provides evidence that more can be done to understand and prevent maternal deaths.  To address the 2010 national health objective of reducing MM to 3.3 deaths per 100,000 live births, this paper reviews the history of MM surveillance in the United States and provides a basis for proposing new strategies that more appropriately address the concerns and issues of the 21st century.