Infant mortality statistics from the 2007 period linked birth/infant death data set.

OBJECTIVES: This report presents 2007 period infant mortality statistics from the linked birth/infant death data set (linked file) by a variety of maternal and infant characteristics. The linked file differs from the mortality file, which is based entirely on death certificate data.
METHODS: Descriptive tabulations of data are presented and interpreted.
RESULTS: The U.S. infant mortality rate was 6.75 infant deaths per 1,000 live births in 2007, not significantly different than the rate of 6.68 in 2006. Infant mortality rates ranged from 4.57 per 1,000 live births for mothers of Central and South American origin to 13.31 for non-Hispanic black mothers. Infant mortality rates were higher for those infants who were born in multiple deliveries; for those whose mothers were born in the 50 states or the District of Columbia; and for mothers who were unmarried. Infant mortality was also higher for male infants and infants born preterm or at low birthweight. The neonatal mortality rate was essentially unchanged from 2006 (4.46) to 2007 (4.42). The postneonatal mortality rate increased 5 percent from 2.22 in 2006 to 2.33 in 2007, similar to the rate in 2005 (2.32). Infants born at the lowest gestational ages and birthweights have a large impact on overall U.S. infant mortality. For example, more than one-half of all infant deaths in the United States in 2007 (54 percent) occurred to the 2 percent of infants born very preterm (less than 32 weeks of gestation). Still, infant mortality rates for late preterm infants (34-36 weeks of gestation) were 3.6 times, and those for early term (37-38 weeks) infants were 1.5 times, those for infants born at 39-41 weeks of gestation, the gestational age with the lowest infant mortality rate. The three leading causes of infant death--congenital malformations, low birthweight, and sudden infant death syndrome--accounted for 45 percent of all infant deaths. The percentage of infant deaths that were "preterm-related" was 36.0 percent in 2007. The preterm-related infant mortality rate for non-Hispanic black mothers was 3.4 times higher, and the rate for Puerto Rican mothers was 71 percent higher than for non-Hispanic white mothers.