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As President Donald Trump has called for an end birthright citizenship, the nation has been experiencing a steep drop in the number of babies born to undocumented immigrant parents, according to Pew Research Center.

About 250,000 babies were born to undocumented immigrant parents in 2016, compared to 390,000 in 2007; a 36 percent drop, the center reported.

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In 2016, babies born to undocumented parents represented about 6 percent of the 4 million births in the country; in 2007, they were 9 percent of total births.

Pew points out that it's important to keep in mind that the immigration status of parents can change over time. There may be parents who had legal permission to be in the U.S. when their child was born but later overstayed their visas, for example. Also, parents may have lacked legal documentation when the child was born but later obtained green cards and citizenship.

Pew estimates that about 5 million children under 18 who were born in the U.S. live with at least one parent who lacks legal status. But that number has "leveled off," Pew notes, due to a decrease in the number of undocumented immigrants following the Great Recession as well as fewer births.

This past week Trump said he would sign an executive order to change birthright citizenship, which is the 14th Amendment of the U.S. Constitution and guarantees that any child born on U.S. soil (with the exception of a child born to diplomats) is a U.S. citizen. Trump said he had the legal power to do this, although most legal scholars disagree.

According to a Sept. 2017 NBC News/Wall Street Journal survey, 65 percent of Americans said birthright citizenship should continue, while 30 percent said it should end.

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