By Moni Basu, CNN
(CNN) – It makes sense that since the start of the recession, the birth rate in America has been declining.
In 2011, it dipped to the lowest rate ever recorded: 63.2 per 1,000 women between 15 and 44, the prime childbearing ages, according to the Centers for Disease Control and Prevention.
That plunge was led by immigrant women, according to a Pew Research Center analysis released Thursday.
The birth rate for U.S.-born women declined 6% between 2007 (when the recession began) and 2010. However, the rate for foreign-born women plunged 14%, more than in the 17 years before the downturn.
Both foreign- and U.S.-born Hispanic women had larger drops in birth rate than any other group, Pew found. That correlates with larger percentage declines in household wealth for Hispanics than in white, black or Asian households.
Among women from Mexico, the country from where the largest number of U.S. immigrants come, the birth rate fell by 23%.
"If you apply the common sense lens here, when it comes to decisions about when to have children, how many and how to space them, the economy clearly matters," said Bill Albert, spokesman for the National Campaign to Prevent Teen and Unplanned Pregnancy.
Even so, Albert warned that any single reason is unlikely to explain an issue as complex as national fertility rates and as profound and personal as the decision to have children.
He said other factors - including people choosing to get married at a later age and a 48% decrease in teen birth rates since their peak in 1991 - may also be playing a role in the decline of the nation's overall birth rate.
The drop reversed a trend in which immigrant mothers were responsible for a rising share of births in the United States, Pew found. In 2007, for instance, foreign-born mothers accounted for 25% of U.S. births, compared with 16% in 1990. In 2010, that share dropped to 23%.
The Pew report's co-author, Gretchen Livingston, said birth rates among foreign-born women have been higher than native-borns for a variety of reasons.
The 2010 birth rate for foreign-born women was 87.8 per 1,000, nearly 50% higher than the rate for U.S.-born women, the Pew report said. Of the 4 million births in America, 930,000 were to immigrants.
Many new mothers are Hispanics, who traditionally have had more children than U.S.-born women, Livingston said.
Immigrants are less educated on average and are more likely to be married. Some bring with them cultural norms from their homelands that can dictate a necessity to have several children.
"What we see with immigrants coming into this country is, they tend to reflect birth rates in their own country," said Robert Walker, president of the Population Institute in Washington.
In some cases, immigrant family sizes can rise as income levels go up in America. The gloomy economy in the past few years has clearly played a role in having fewer children, he said.
Among the Pew study's other findings:
• A majority of births to U.S.-born women (66%) in 2010 were to white mothers, while the majority of births to foreign-born women (56%) were to Hispanic mothers.
• Teens account for a higher share of births to U.S.-born moms (11% in 2010) than to immigrants (5%). That number is linked to the age profile of immigrants.
• Immigrant women accounted for fully 33% of births to women 35 and older in 2010.
Livingston pointed to how the overall birth rate of the United States has stayed relatively constant compared with that of some European nations that have experienced declining populations. Immigrant women in America, she said, have held that number up.
The Pew Research Center's projections indicate that immigrants will continue to play a large role in U.S. population growth: Immigrants arriving since 2005 and their descendants will account for 82% of U.S. population growth by 2050.
The report said this about the future: "Even if the lower immigration influx of recent years continues, new immigrants and their descendants are still projected to account for most of the nation’s population increase by mid-century."
It's difficult to say how birth rates will be affected when the economy improves and people feel fatter in their pocketbooks. Population experts say it's a fair assumption that the birth rate may go up again. One thing is for sure: The face of America will look very different in a few decades.