Changes in cesarean delivery rates by gestational age: United States, 1996-2011.

Data from the natality data file, national vital statistics system. After 12 years of consecutive increases, the preliminary cesarean delivery rate among singleton births was unchanged from 2009 to 2011 (31.3%). Cesarean delivery rates decreased more than 5% among births at 38 weeks of gestation, but increased 4% among births at 39 weeks. Decreases in cesarean delivery rates for births at 38 weeks occurred for non-Hispanic white, non-Hispanic...