Louisiana, Mississippi and Alabama have highest rate of premature births

One in nine U.S. babies is born prematurely, and more than 450,000 are born too soon each year, says the March of Dimes 2014 Premature Birth Report Card, which gave each state a letter grade for how well they fare on premature births.

The South scored the lowest, with Louisiana, Mississippi and Alabama all receiving an "F," while Florida and South Carolina were given a "D." Overall, the U.S. received a "C," with 19 states—most of them largely rural—getting a "C," while 21 states were given a "B" and five an "A." (Read more) (March of Dimes map)