Proportion of prenatal visits seen in hospital outpatient departments compared to obstetrician's offices in high and low medical liability regions, 1997–2004. National estimates based on 21,454 visits in the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey. High medical liability risk region is comprised of states in the Northeast and South. Low medical liability risk region is comprised of states in the Midwest and West. For trend: P < .001 for high liability risk region and P = .012 for low liability risk region.