The number of children born in the United States to undocumented immigrants has dropped by about 20 percent since its 2007 peak after rising sharply for a quarter-century, the Pew Research Center said on Friday.
An analysis of Census Bureau data by the polling group showed that about 8 percent of the nearly 4 million births in the United States in 2013 had at least one parent who was living in the country illegally.
Children of undocumented immigrants became a prominent issue in the race for the White House after U.S. Republican presidential hopeful Jeb Bush used the phrase "anchor babies" in a radio interview last month and was criticized by other presidential candidates for doing so.
Immigration critics sometimes use the term "anchor babies" to describe U.S.-born children of illegal immigrants. Immigration groups say the phrase is offensive.
The 14th Amendment to the U.S. Constitution grants citizenship to any child born on U.S. soil, regardless of parentage.
About 295,000 babies were born to parents who were unauthorized immigrants in 2013, down from 370,000 in 2007, Pew said.
Some Republicans seeking the presidential nomination, including Donald Trump, have criticized across-the-board birthright citizenship.
About 11.3 million unauthorized immigrants lived in the U.S. in 2013, making up 4 percent of the population, Pew said. It said their share of total births is higher because the immigrants include a greater share of women in their childbearing years and have higher birthrates than the overall U.S. population.
Most children of unauthorized immigrants in the United States are born here and thus are citizens, Pew said. Unauthorized immigrants are more likely than in the past to live with U.S.-born children and to be long-term U.S. residents, Pew said.
There were 4.5 million U.S.-born children younger than 18 living with parents who were unauthorized immigrants parents in 2012, Pew said.