Birth rates are climbing after years of significant declines, according to a report released Monday in the journal Pediatrics.

Birth rates are climbing after years of significant declines, according to a report released Monday in the journal Pediatrics.

Researchers from the Centers for Disease Control and Prevention found that the number of U.S. births for 2007 had jumped 1 percent to 4,265,555, “the highest number ever registered for the United States,” they said. Almost 1.9 million people joined the population due to “natural increase,” which is basically the net birth rate.

As the birth rate rose, the age-adjusted death rate dropped 2.1 percent, a record low for the U.S. Life expectancy at birth reached a record high of 77.9 years.

One shocker: The U.S.’ infant-death rate is 6.83 per 1,000 births. Compare that with Malaysia (6.2) or Korea (3.8). And in the U.S. capital, the District of Columbia? It’s nearly double the national rate, at 12.22.

Younger mothers, particular adolescents, pushed the birth rate higher. From 1991 to 2005, teen birth rates dropped 34 percent. Since 2005, though, they’ve popped back up 5 percent.

“The recent increase was preceded by the slowing decline but, nonetheless, caught … the public-health community somewhat by surprise,” the study said.