The U.S. has earned a grade "C" for its preterm birth rate on the new March of Dimes Premature Birth Report Card, Philly.com reports.

The country has a preterm birth rate of around 10 percent.

Among 100 American cities with the most births, Shreveport, La., scored an "F" on the report card for its preterm birth rate of almost 20 percent in 2013,

Portland, Ore., Oxnard, Calif., St. Paul, Minn., and Seattle earned an "A" for their low preterm birth rates.

The report card, released Nov. 5, is based on data from the U.S. National Center for Health Statistics.

"Reaching our goal ahead of schedule is progress, but it is not victory -- our work is far from done," Dr. Jennifer Howse, president of the March of Dimes, said in a news release from the group.

"As our new list of city preterm birth rates highlights, many areas of the country, and tens of thousands of families, are not sharing in this success. No baby should have to battle the health consequences of an early birth. All babies, everywhere, deserve a healthy start in life," Howse said.

With its 2014 preterm birth rate, the United States met the March of Dimes 2020 goal early.

However, preterm birth still remains the leading cause of infant death in the United States.

The report also emphasized the belief that racial and ethnic disparities may be partially responsible for high preterm birth rate. Overall, black women had the highest percentage of preterm births while Asian had the lowest percentage, Newsweek reports.

The March of Dimes also the goal of reducing the nation's preterm birth rate to about 8 percent of live births by 2020 and to 5.5 percent by 2030.

"This aggressive goal can be achieved by increasing best practices in preconception and pregnancy care, wider use of proven interventions such as progesterone and birth spacing, and funding discovery research through our research centers," Howse said.

According to the March of Dimes, a premature baby is one who is born before 37 weeks. Around one out of every 10 babies is born premature across U.S each year, Medical Daily reports.