The number of U.S. children who died in 2011 within a year of birth in 2011 declined 12 percent from 2005, as fewer babies are born prematurely, health authorities reported.
Six in 1,000 children died within their first year in 2011 compared with 6.9 per 1,000 in 2005, according to the Centers for Disease Control and Prevention.
The number of children who die in their first year is often used as an indicator of health in a country. In 2008, the U.S. infant mortality rate was ranked 27th globally in a report from the Organization for Economic Cooperative Development. Even with the improvement since 2005, the U.S. likely still ranks 27th, according to the report from the Atlanta-based CDC.
"We should feel pretty proud about this, because it takes a lot to change population statistics," said Carol Miller, a clinical professor of pediatrics at the University of California, San Francisco. She wasn't involved in the report. "We've been struggling with this issue for quite some time."
The highest estimated rate of infant mortality in 2012 worldwide was in Afghanistan, at a rate of 121 children per 1,000 births; the lowest was Monaco, with 1.8 deaths occurring per 1,000 births, according to the Central Intelligence Agency. The CIA estimates that 6 children per 1,000 live births died in the U.S. last year, a higher rate than Canada or the U.K.
The leading cause of infant death in the U.S. was birth defects, followed by premature births. Newborns are considered to be full term after 40 weeks of gestation. Those health issues, along with sudden infant death syndrome, maternal complications and unintentional injuries accounted for more than half of the infant deaths in 2011.
"We've seen a recent decline in preterm births, which is good because babies who are born too soon have much higher infant mortality rates," said Marian MacDorman, a senior statistician at the National Center for Health Statistics in Hyattsville, Md., and a study author. "One thing we think helped the preterm birth situation was trying to prevent medical interventions such as early C-sections and inductions."
The cut in the U.S. infant mortality rate was most rapid in Southern states. Georgia, Louisiana, North Carolina, South Carolina and the District of Columbia had a decline of 20 percent or more in their rates in 2010 compared with 2005, when they had been "persistently high" for "many years," according to the report.
While no states had a significant increase in infant deaths, babies were more likely to die after birth in Mississippi and Alabama, which had mortality rates of 8 per 1,000 infant births or higher. Data for individual states in 2011 isn't yet available.
Infant mortality rates declined most for babies born to black women, dropping 16 percent. Historically, infants have been twice as likely to die in their first year if their mothers are black compared with those born to white mothers, according to the CDC's report.
The higher rates are likely tied to less access to quality care, poor health, a lack of education about good health practices, and discrimination, Miller said.