Birthrates in the United States are dropping, and one study links the decline to the U.S. recession.

A Pew Research Center study released Wednesday shows a birthrate in decline since 2007 -- a year with a record number of births in the U.S. -- matches up with a drop in income.

In 2007, there were 4.3 million births in the U.S. After the near-collapse of the economy, provisional data shows that there were just over 4 million births in 2010, according to the study.

The study also detected a correlation between the economy and birth rate in individual states. North Dakota, for instance, in 2008 had a 3.1 percent unemployment rate, one of the lowest in the U.S. The state saw a slight increase in births from 2008 to 2009, the study said.

In 48 out of 50 states, plus Washington D.C., fertility declines occurred within a year or two of the start of economic downturns, Pew said.