The U.S. preterm birth rate (less than 37 weeks of gestation) rose by more than one-third from the early 1980s through 2006 (1). This rise has been a cause of great concern (2,3). Preterm infants are at increased risk of life-long disability and early death compared with infants born later in pregnancy (2,4). Many reasons, such as changes in maternal demographics and increases in multiple births, have been suggested for the growth in preterm births (5). Another factor cited is the heightened use of obstetric interventions such as induction of labor and cesarean delivery earlier in pregnancy (5,6,7). Although it is not possible to know whether an infant would be born preterm if labor was not induced or delivered by cesarean, studies suggest that increased use of these procedures before 37 completed weeks of gestation may have influenced the upswing in preterm birth rates (6,7). Preliminary 2007 and 2008 birth certificate data reveal a shift in the long upward trend in preterm births (8,9). This report describes this change
