More than a half million babies were born too soon in the United States in 2004, the most recent year reported, according to preliminary data released by the National Center for Health Statistics.

Some 12.5 percent of all babies - about 508,000 - were born premature (less than 37 completed weeks gestation) according to Preliminary Births for 2004: Infant and Maternal Health.

"We were deeply saddened to learn these sobering statistics," said Dr. Jennifer L. Howse, president of the March of Dimes. "Prematurity has reached crisis proportions, and has become the number one killer of newborns. The health consequences for babies who survive can be devastating. We must renew our commitment today to raise public awareness about prematurity, and to mobilize the political will to act."

Each year, about 1 in 8 live births are premature. The latest statistics represent a nearly 2 percent increase over 2003 final data. The preterm birth rate has increased 33 percent since 1981, the first year the government began tracking premature birth rates. There's been an 18 percent increase since 1990, according to the report.

Prematurity is the leading cause of death in the first month of life, and those who survive often have serious lifelong health problems such as cerebral palsy, mental retardation, chronic lung disease, blindness, and hearing loss. As much as half of all neuro-developmental problems in children can be attributed to premature birth.

Also, more babies were born with low birthweight (less than 5.5 pounds) in 2004, according to the government report. The rate of low birthweight babies reached 8.1 percent, up from 7.9 percent in 2003, a nearly 16 percent increase since 1990.

The March of Dimes Prematurity Campaign, which began in 2003, seeks to educate women on the signs and symptoms of premature birth, and to support more medical research into the causes of premature labor. One of the goals of the campaign is to help the nation reach the goal set by the U.S. Public Health Service of reducing the rate of premature birth to 7.6 percent by 2010.

For more information on the March of Dimes, visit www.marchofdimes.org or its Spanish language Web site at www.nacersano.org.