The U.S. birth rate has dropped for the second year in a row, and experts think the recession led many people to put off having children. The 2009 birth rate also set a record that was the lowest in a century.

Births fell 2.7 percent last year even as the population grew, numbers released Friday by the National Center for Health Statistics show.

The birth rate, which takes into account changes in the population, fell to 13.5 births for every 1,000 people last year. That’s down from 14.3 in 2007 and way down from 30 in 1909, when it was common for people to have big families.

The situation is a striking turnabout from 2007, when more babies were born in the United States than any other year in the nation’s history. The recession began that fall, dragging stocks, jobs ,and births down.

Another possible factor in the drop: a decline in immigration to the United States.

The downward trend invites worrisome comparisons to Japan and its lost decade of choked growth in the 1990s and very low birth rates. Births in Japan fell 2 percent in 2009 after a slight rise in 2008, its government has said.

Not so in Britain, where the population took its biggest jump in almost half a century last year and the fertility rate is at its highest level since 1973. France’s birth rate also has been rising; Germany’s birth rate is lower but rising as well.

The new U.S. report is a rough count of births from states. It estimates there were 4,136,000 births in 2009, down from 4,251,095 in 2008 and more than 4.3 million in 2007.

Last spring’s report, on births in 2008, showed an overall drop but a surprising rise in births to women over 40, who may have felt they were running out of time to have children and didn’t want to delay despite the bad economy.

The Associated Press contributed to the report.