This is double the risk of earlier estimates by experts.
Joann Petrini, director of the March of Dimes' Perinatal Data Center, said, "We have long known that babies born too soon face many challenges -- even death. But this research confirms the urgent role preventing preterm birth can play in improving infant mortality in the United States."
Their findings were published in the October issue of the journal Pediatrics.
An inexplicable discrepancy in infant mortality statistics in the United States led to the CDC study. Estimates in 2002 by the National Center for Health Statistics showed that 17 percent of infant deaths were linked to premature birth. However, these statistics revealed that two-thirds of infant deaths that year were of babies who had been born prematurely.
This led the CDC researchers to infer that the official reporting system may not give the actual impact of prematurity in infant deaths.
Therefore their analysis used a different methodology. Therefore while looking at infant deaths they included prematurity as well as other conditions like respiratory distress syndrome commonly occurring in "preemie" babies.
With this approach, the CDC team concluded that prematurity was the underlying cause of 34.3 percent of infant deaths in 2002. The researchers added that over 95 percent of those deaths involved premature babies born at less than 32 weeks' gestation.
These results have led to researchers suggesting that prematurity supplants birth defects as the leading cause of infant deaths in the United States.
On the whole U.S. infant mortality has been known to decline steadily since 1995, except between 2001-2002 -- the first rise since 1958. Over 500,000 U.S. babies are born too soon each year, with experts saying that the rate for preterm births has jumped more than 30 percent since 1981.
Premature births not only increases infant-mortality risks, but has also raised a child's risk for chronic lung disease, mental retardation, vision/hearing problems, as well as other developmental problems.