The drop in U.S. birth rates after the onset of the Great Recession was led by foreign-born women, whose birth rates plunged 14% from 2007 to 2010, according to a new Pew Research Center analysis of government data. The overall birth rate declined 8% in those years, and the birth rate for U.S.-born women decreased 6%.

According to the National Center for Health Statistics, the preliminary 2011 overall birth rate—the annual number of births per 1,000 women in the prime childbearing ages of 15 to 44—was the lowest since at least 1920, the first year for which there are reliable numbers. (Final data, and information about whether mothers are immigrants or U.S. born, are not available for 2011.) The U.S. birth rate, which had been relatively stable since the mid-1970s, began to fall after 2007, the year the Great Recession began.

In addition to the decline in birth rates, the number of U.S. births also fell abruptly after 2007, a decline led by immigrant women as well. From 2007 to 2010, the overall number of births declined 7%, but births to foreign-born mothers fell 13% while births to U.S.-born women decreased only 5%.

Total births in 2010 were 4.0 million, including roughly 3.1 million to U.S.-born women and 930,000 to immigrant women. (In 2011, according to preliminary data, there were 3.95 million total births.)

The recent downturn in births reversed a trend in which foreign-born women accounted for a rising share of U.S. births—16% in 1990 to 25% in 2005-2007, but 23% in 2010.

The report concluded that the decline in foreign-born fertility was due to declining birth rates, and not to any reductions in the number of immigrant women of childbearing age. The report does not address the reasons why women had fewer births after 2007, but previous Pew Research analysis has found links between fertility decline and economic distress.

The new report also includes a comparison of demographic characteristics of U.S.-born and foreign-born mothers, by age, race, ethnic group and marital status. Birth rate declines were especially sharp for Mexican immigrant women (down 23% from 2007 to 2010).

The report, “U.S. Birth Rate Falls to a Record Low; Decline is Greatest Among Immigrants,” used data from the National Center for Health Statistics and Census Bureau.