The Trump administration on Thursday announced new visa rules to restrict birth tourism, in which women travel to the United States to give birth so their children can get US citizenship.

According to the rules in the Federal Register, applicants will not be given tourist visas if they are determined by consular officers to be coming to the US only to give birth.

It is a bigger hurdle to overcome, proving they are travelling to the US because they have a medical need and not just because they want to give birth here. Those with medical needs will be treated like other foreigners coming to the US for medical treatment and must prove they have the money to pay for it including transportation and living expenses.

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“Closing this glaring immigration loophole will combat these endemic abuses and ultimately protect the United States from the national security risks created by this practice,” White House press secretary Step­hanie Grisham said in a statement.

While the new rules deal specifically with birth tourism, the Trump administration also has turned away pregnant women coming over the U.S.-Mexico border as part of a broader immigration crackdown. Those women were initially part of a vulnerable group that included others like small children who were allowed in, while tens of thousands of other asylum seekers have been returned to Mexico to wait out their cases.

While President Trump’s administration has been confining all forms of immigration, Trump has been particularly worried by the issue of birthright citizenship anyone born in the US is considered a citizen, under the Constitution.

The Republican president has criticized the practice and threatened to end it, but scholars and members of his administration have said it’s not so easy to do.

Regulating tourist visas for pregnant women is one way to get at the issue, but it raises questions about how officers would determine whether a woman is pregnant, to begin with and whether a woman could get turned away by border officers who suspect she maybe just by looking at her. Critics of the new policy say it could put pregnant women at risk.