"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.
"It could take a few years to turn this around," he added.
Despite this drop, there are still 2 million more people born each year in the US than there are people dying and the death rate has been dropping. Indeed, the infant mortality rate declined between 2007 and 2009 so a slightly higher fraction of the babies born in 2009 will survive compared to 2007.