Cesarean birth in the United States: epidemiology, trends, and outcomes.

The percentage of United States cesarean births increased from 20.7% in 1996 to 31.1% in 2006. Cesarean rates increased for women of all ages, race/ethnic groups, and gestational ages and in all states. Both primary and repeat cesareans have increased. Increases in primary cesareans in cases of "no indicated risk" have been more rapid than in the overall population and seem the result of changes in obstetric practice rather than changes in the medical risk profile or increases in "maternal request." Several studies note an increased risk for neonatal and maternal mortality for medically elective cesareans compared with vaginal births.