Born a bit too early: recent trends in late preterm births.

KEY FINDINGS The U.S. late preterm birth rate rose 20% from 1990 to 2006. If the late preterm rate had not risen from the 1990 level, more than 50,000 fewer infants would have been delivered late preterm in 2006. On average, more than 900 late preterm babies are born every day in the United States, or a total of one-third of 1 million infants (333,461). Increases in late preterm births are seen for mothers of all ages, and for non-Hispanic white and Hispanic mothers. The rate for black mothers declined during the 1990s, but has been on the rise since 2000. Late preterm birth rates rose for all U.S. states, but declined in the District of Columbia. The percentage of late preterm births for which labor was induced more than doubled from 1990 to 2006; the percentage of late preterm births delivered by cesarean also rose markedly.