Babies born just a few weeks premature are six times more likely to die during their first week of life and three times more likely to die before their first birthday than full-term babies, a U.S. study finds.

According to the March of Dimes Foundation, late preterm babies (born at 34 weeks to 36 weeks gestation, compared to 37 weeks for full-term babies) account for 71 percent of the more than 500,000 premature births each year in the United States.

Late preterm infants have greater risk of certain problems like respiratory distress syndrome (RDS), feeding difficulties, temperature instability (hypothermia), jaundice and brain development according to earlier studies.

"Now, we have evidence that there is a greater risk of death among these babies," Dr. Jennifer L. Howse, president of the March of Dimes Foundation said in a press release.

Suggesting that the babies born even just a few weeks too soon should be closely monitored, the report said that the national preterm birth rate is 12.5 percent which means that more than 500,000 infants are born too soon each year.

The release of report coincides with Nov. 13, which is marked as Prematurity Awareness Day in the United States. The leading cause of death is birth defects, with preterm infants about four times more likely than full-term babies to die of congenital deformities.