WASHINGTON (AP) -- The odds of having a premature baby are lowest in Vermont and highest in Mississippi. The March of Dimes mapped the stark state-by-state disparities in what it called a "report card" on prematurity Wednesday -- to track progress toward meeting a federal goal of lowering preterm births.

There's not much chance of meeting that goal by the original 2010 deadline, if the "D" grade the charity bestowed on the nation is any indication.

More than half a million U.S. babies -- one in every eight -- are born premature each year, a toll that's risen steadily for two decades. The government's goal: No more than 7.6 percent of babies born before completion of the 37th week of pregnancy.

Preterm birth can affect any mother-to-be, stressed a recent U.S. Surgeon General's meeting on the problem. Scientists don't understand all the complex causes.

But Wednesday's report highlights big geographic differences that March of Dimes president Dr. Jennifer Howse called "a dash of cold water."

In Vermont, 9 percent of babies were preemies in 2005, the latest available data. In Oregon and Connecticut, just under 10.5 percent of babies were premature.

Travel south, and prematurity steadily worsens: In West Virginia, 14.4 percent of babies were preemies; more than 15 percent in Kentucky and South Carolina; more than 16 percent in Alabama and Louisiana; and a high of 18.8 percent in Mississippi.

The report urges states to address three factors that play a role:

-Lack of insurance, which translates into missed or late prenatal care. In states with the highest prematurity rates, at least one in five women of childbearing age are uninsured. Early prenatal care can identify risks for preterm labor and sometimes lower them.

-Smoking increases the risks of prematurity, low birthweight and birth defects. Government figures suggest 17 percent of women smoke during pregnancy. The new report urged targeting smoking by all women of childbearing age. About a third of those women smoke in Louisiana and West Virginia, the report says, compared with 9.3 percent and 11 percent in Utah and California, respectively.

-Then there's the trickier issue of so-called late preemies, babies born between 34 and 37 weeks. They're fueling the nation's prematurity rise. While not as devastating as a baby born months early, being even a few weeks early can cause learning or behavioral delays and other problems. And recent research suggests at least some near-term babies are due to Caesarean sections scheduled before full-term, either deliberately or because of confusion about the fetus's exact age.

Howse urged hospitals to double-check that women given an early C-section truly need one for a medical problem, as current health guidelines recommend.

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