Some people oppose the application of birthright citizenship to children of illegal immigrants. Some argue citizenship is not guaranteed by the Fourteenth Amendment to the children of illegal immigrants, but this interpretation has never been endorsed by federal courts. The Pew Hispanic Center estimates that approximately 7.5% of all births in the U.S. (about 300,000 births per year) are to unauthorized immigrants. The Pew Hispanic Center also estimates that there are 4.5 million children born to unauthorized immigrants who received citizenship by birth in the United States, while the Migration Policy Institute estimates that there are 4.1 million children. Both estimates exclude anyone 18 and older who might have benefited. On January 24, 2020, the Trump administration adopted a policy to make it more difficult for pregnant foreign women to come to the US where it is suspected that the purpose is to give birth on US soil and thereby to ensure their children become US citizens, a practice commonly called "birth tourism".