The birth rate in the United States is at its lowest level in 100 years, according to numbers released Friday by the National Center for Health Statistics.

The report estimated there were 4,136,000 babies born last year and nearly a 3 percent drop from 2008.

"It's a good-sized decline for one year. Every month is showing a decline from the year before," said Stephanie Ventura, the report's demographer.

In 2007, more babies were born in the U.S. than any other year in the country's history. The recession began during the fall of that year, bringing down stocks, jobs, and births.

"When the economy is bad and people are uncomfortable about their financial future, they tend to postpone having children. We saw that in the Great Depression the 1930s and we're seeing that in the Great Recession today," said Andrew Cherlin, a sociology professor at Johns Hopkins University.

Experts say more couples are putting off having children, because of the economy. They also point to a decline in immigration.