Dr. Jennifer L. Howse, president of the March of Dimes, said the national preterm birth rate peaked in 2006 at 12.8 percent after rising steadily for more than two decades. However, the 2012 rate was a 10 percent improvement since the 2006 peak and the best rate since 1998.
"Although we have made great progress in reducing our nation's preterm birth rate from historic highs, the United States still has the highest rate of preterm birth of any industrialized country," Howse said in a statement. "A premature birth costs businesses about 12 times as much as uncomplicated healthy birth. As a result, premature birth is a major driver of health insurance costs."
The Institute of Medicine said preterm birth -- before 37 weeks of pregnancy -- costs the United States more than $26 billion annually, Howse said.
It is the leading cause of newborn death, and babies who survive an early birth often face the risk of serious and sometimes lifelong health problems, such as breathing problems, jaundice, developmental delays, vision loss and cerebral palsy.
Even infants born at 37-38 weeks of pregnancy have an increased risk for health problems compared to infants born at 39 weeks, Howse said.
Six states: Alaska, California, Maine, New Hampshire, Oregon and Vermont earned an "A" on the March of Dimes Premature Birth Report Card as their preterm birth rates met the March of Dimes 9.6 percent goal.
Nineteen states earned a "B," 17 states and the District of Columbia received a "C," five states got a "D," and three states and Puerto Rico received an "F" on the report card.