HYATTSVILLE, MARYLAND — After significant declines in the 20th century, the U.S. infant mortality rate plateaued from 2000-05 but declined again from 2005-11, officials say.

Marian F. MacDorman, Donna L. Hoyert and T.J. Mathews of the National Center for Health Statistics, part of the Centers for Disease Control and Prevention, found in 2005 the infant mortality rate was 6.87 infant deaths per 1,000 live births, not significantly different from the rate of 6.91 in 2000.

Subsequently, the U.S. infant mortality rate declined significantly from 2005-06, but did not change significantly from 2006-07, and then declined significantly each year from 2007 through 2010, the report said.

In 2011, the U.S. infant mortality rate was 6.05 infant deaths per 1,000 live births, 12 percent lower than the rate of 6.87 in 2005.

From 2005 through 2011, the neonatal mortality rate — deaths under age 28 days per 1,000 live births — declined 11 percent and the post-neonatal mortality rate — deaths at ages 28 days to under 1 year per 1,000 live births — declined 14 percent.