Preterm births - United States, 2006 and 2010.

Approximately one third of all infant deaths in the U.S. are related to preterm birth. Infants who survive a preterm birth are at greater risk than those born later in pregnancy for early death and lifelong effects such as neurologic and cognitive difficulties. The rate of preterm births (i.e., <37 completed weeks' gestation) increased approximately 30% during 1981-2006. In 2007, this trend began to reverse; the U.S. preterm birth rate decreased for the fourth consecutive year in 2010, decreasing from the 2006 high of 12.8% to 12.0% in 2010. A total of 4,265,555 births were reported for 2006, including 542,893 preterm births, and 3,999,386 births were reported for 2010, including 478,790 preterm births. Although most of the recent decrease in this rate was among infants born at 34 to 36 weeks' gestation (i.e., late preterm), with a decrease from 9.15% to 8.49% during 2006-2010, the rate of infants born at <34 weeks' gestation (i.e., early preterm) also decreased from 3.66% in 2006 to 3.50% in 2010. Despite improvements in the rate of preterm births, the total number of infants born preterm remains higher than any year during 1981-2001. Substantial differences in preterm birth rates by race/ethnicity persist; additional examination of these differences can provide insight into potential areas for interventions.